Let me start this one by saying what you're already thinking ... "Who in the HELL does he think he is to tell ME how to sell more art?"  Am I right? 
Well ... after many years of visiting art galleries, interviewing artists, buying art online and basically being obsessed with contemporary art and finding ways to make it more accessible to everyone, I've boiled this complicated issue down to the basics.  
In our complex, sophisticated and often convoluted world, we often dismiss the basics.  That's understandable because the world is multi-layered and everything is inner-connected; fiddling with something here messes up something over there.  Still, didn't Leonardo da Vinci or Charles Eames or someone say, "Simplicity is the ultimate sophistication"? 
Let me also say that I'm writing this during Black Friday, certainly the one day of the year when nearly everyone is thinking about retail, even if they're avoiding their local mall like the plague (which I'm doing).  Haven't you heard that art is retail?  With all of that in mind, using Black Friday as my model, here are what we'll call  ... 5 Ways to Sell More Art ...
1. PRICE TO SELL: Let's get straight to the point.  Galleries, artists and online art venues have GOT to get REAL.  Just so you know, retail analysts say Black Friday alone rings up $60 billion in sales for retailers.  Black Friday is a master class in marketing and sales.  How do retailers move their merchandise?  By putting it ... ON SALE.  This is the very same stuff that's on store shelves year round.  Putting an item on sale is the equivalent of giving it cardio pulmonary resuscitation.  This is such a no brainer.  Put art on sale!  The art world has got to realize that, YES, art is retail.  I know.  I know.  Art is precious, profound and above reproach.  How dare I speak about art in such a lowly way ... like some street corner huckster.
However, it's because I revere and respect art so much that I'm speaking this way.  I believe that far too many galleries and artists, yes artists, have their heads stuck in the clouds and they refuse to see simple reality.  MAKE ART AFFORDABLE. 
I am NOT saying that artists should give their work away.  I am also NOT saying that galleries should slash prices to the point of losing money.  NO.  What I am saying is that most galleries have certain, select buyers that keep them going.  Why not expand your client base by pricing work strategically and assertively - not aggressively, you don't want to GIVE it away.   Why not experiment and find your "sweet spot" when it comes to pricing, especially around holiday time?
Also, why not put prices on your merchandise?  People NEED to know prices.  They shouldn't have to risk humiliation by asking.  You know, galleries are basically museums that sell art.  Problem is ... most galleries don't want to be seen as "too commercial."  They don't necessarily want to be seen as "stores," but the fact remains that galleries exist to sell art.  Believe it or not, but I visited galleries for years before it truly occurred to me that yes, galleries exist primarily to SELL art.  Galleries need to make that VISIBLY clear in their spaces.  This can indeed be done with class, style and without appearing like you're a convenience or department store. 
Once again, artists and galleries need to get creative like the fashion industry.  Why not create various lines of art at various price points?  Also, why not sell more affordable drawings, prints, gouaches and lithographs of artists' works in addition to their more expensive paintings in the very same space?  Give people OPTIONS.
Most galleries want to be thought of as "upscale."  Again, galleries are not Walmart nor are they Target.  However, you know as well as I do that there's not an art gallery nor artist on God's earth that wouldn't practically sell the farm to move merchandise like the big name retailers do.  Am I right?  Wouldn't that be great?
So many galleries are obsessed with wanting to appear "upscale" and discriminating to their very detriment.  Yet, what's the point in pricing art so high that it doesn't sell?  Again, I want art galleries and artists to make as much money as they possibly can, but let's also use some common sense here.  Much of the art you see in galleries never sells.  It doesn't have to be this way.
One final thing about pricing art to sell.  Most consumers all over the world have been conditioned to buy things that are "on sale."  People are not stupid. No one with a brain wants to pay more than they need to for anything.  This includes wealthy people along with art dealers and certainly gallery staffers.  Why not use your own common sense when it comes to selling art?
Let me add this ... when art sells, it sets into motion a chain of positive energy that reverberates well beyond gallery walls.  It affects the art gallery, assistants, art handlers, artists, collectors, the family and friends of art buyers and the general public.  This totally opens the world to the possibilities of contemporary art.  Think about that.
2. PROMOTE, PROMOTE, PROMOTE: I swear, if I see one more Macy's or Target commercial, I'm going to croak.  And guess what?  It's only Black Friday.  The Christmas shopping season has just begun.  Big name retailers are masters at marketing and promotion.  But when have you EVER heard an art gallery say it's having an art sale?  I mean a TRUE art sale.
It's not very feasible for independent artists and art galleries to do television commercials, but they do have so many venues they can exploit.  Namely art publications and most importantly, social media which - at this moment - remains completely free of charge.  I'm on social media every day and I've yet to see any artist or gallery truly use it to their best advantage.  Sad. 
What I'm saying here is that 99% of human beings aren't mind readers.  Artists, how are people going to KNOW you have art for sale unless you TELL them?  It simply amazes me how quiet and mousy the art community continues to be.  Art galleries have got to make some noise!  Let people know that you exist.
Artists, one more thing for you.  It's no longer acceptable for you to use your creativity and artistry as an excuse to avoid marketing and promotion.  The most successful artists - Warhol, Picasso, Lichtenstein, etc. - constantly got out there and promoted their work.  Actors promote their upcoming films and theater projects in the public domain.  So do singers who release new music.  Artists, WHERE ARE YOU?
3. EDUCATE PEOPLE: One of the things that I admire about big name retailers along with professional sports organizations is that they're constantly informing (or shall I say mentally conditioning) the general public.  It's usually subliminal and highly effective.  At the very least, most everyone knows where their local mall and sports arenas are located.  Do most people even have a clue about the closest art gallery in their community?  I doubt it.
The lack of arts education in schools and in the public domain means that art galleries and arts councils really need to combine efforts and share the burden of educating the public about art.  How about at least letting people know where to find you?  Why can't a bunch of galleries get together and offer interested people low-cost classes that teach the basics about contemporary art and collecting?  These can start as hour-long classes that give folks the basics.
4. EXPAND YOUR AUDIENCE: "Art for all People" is ArtBookGuy's federally-registered trademark.  What it means is that art isn't only for the rich.  Art is literally created by all kinds of people FOR all kinds of people.  Sure, wealthy clients spend lots of money on blue chip art, but blue chip art is a shrinking pool.  Contemporary art continues to be created every single day by gifted artists all over the world.  Isn't it time to truly tap into that vast ocean by considering most people potential art buyers?  On Black Friday, most retailers assume that most everyone can be enticed to go out and spend money.  I would say this strategy has been paying off fairly well for them.  No?
5. CUT THE SNOBBERY: Whenever people ask me about art, I always get this feeling that they're very suspicious of it.  Since most people don't know much about contemporary art, they tend to jump to conclusions and rather than buy into art, they buy into stereotypes.  Sad.  Unfortunately, many people in the art world don't help much.  Their very behavior often supports the stereotypes.
Along those lines, years ago, a former colleague told me that his girlfriend really wanted to attend a local art museum event during the weekend, but he didn't want to go.  He told me that he really didn't want to spend a single moment with "those art snobs." Just between us, I think he was also taking a jab at me because he knew I'm really into contemporary art.   Given that, I worked hard and finally convinced him that he should go.  I told him that not everyone in the art world is a "snob."
Well ... sure enough, come Monday, my colleague came over to me and said, "Mike, I couldn't believe those stuck up assholes!  Are THOSE the kind of people you hang out with?" 
Needless to say, after working hard to convince him otherwise, I won a convert and then lost a convert.  All within 72 hours.  The closed, cliquish atmosphere of the art world is quite unfortunate.  By the way, even in the current shaky economy, my former colleague can certainly afford to buy art.  Guess it'll never happen now.
Consider those your "5 Ways to Sell More Art."  But first ...
In closing, let me just say that selling art is not easy and there's no quick fix for decades and decades of sloppy and unfortunate precedent.  Let's face it.  Most people don't NEED art and they're certainly not going to buy a painting before they purchase an iPad, pair of designer shoes or new car.  It just troubles me that the art world often puts up barriers that make the situation even more difficult.
Years ago, I was visiting an art gallery in Chicago with an artist friend.  Needless to say, the gallery was quiet except for us, so I had plenty of time to chat with the gallery owner whose name I won't reveal.
Anyway, this was just after the economy tanked in 2008 or thereabouts.  I said to the gallery owner, "This is such a hard time with the economy and all.  I bet things really 'suck' for you now."
The gallery owner replied, "Yeah, but it always sucks!"  We all laughed.
Yet, as I recall that cool art gallery visit with that very cool gallery owner, all I can think now is ...
"Do things really have to ALWAYS suck?"    

8 Ways the Art World Swindles People