Hmm…I don’t print my art for a particular person. I simply make it because I like making it and it’s a style I like, it just comes naturally to me- luckily it just so happens that other people like it as well. I haven’t changed anything I do to suit any particular person/audience and as such a customer base has built around me, and I’ve had returning customers due to people buying something for themselves wanting more and/or wanting gifts for other people.
I started selling online last year (on various websites) as well as in B&M shops and to date I’ve sold about 80 prints. I’ve got no idea if that’s good or not- but I have no target to meet.
I do promote what I do- but not as much as I used to. I use Facebook, Twitter and Instagram- I probably find Instagram and Facebook the best- my Twitter promoting has been quite bad for the last few months actually. I don’t tend to seek out customers: I just do what I do and hope that people find me- and so far they do.
I guess it depends what you create. I think Art is a one that shouldn’t be made to grab an audience- because then it doesn’t come naturally- art should simply be creating your own style and finding your own niche.
Other products, let’s say knitted products for example; they probably have to follow fashion trends to sell? (Though not sure- I don’t buy one off knitwear) but then I think it probably would matter where you advertise. Who buys your product & where from.
I think craft fairs are good- to an extent- remember at craft fairs you will only get people who actually like craft fairs! Very female heavy & traditionally middle aged+. Also- depending on where it is, might determine how much the average customer wants to spend. So you’re still only going to get a glimpse of a limited audience.
Facebook is probably a good bet- as a huge amount of people are on that. It tells you the demographics for who is following your page as well- male/female, age, location. Though if you pay to promote on their from what I gather from other people it becomes a totally different thing (and doesn’t sound worth it)
Instagram was initially attractive to younger people; though now it seems to be opening out and more of an age range use that app. Personally I find it a really friendly & supportive network. It’s gotten me some really decent commissions for other companies as well.
Twitter I’d say is a big mix- though I wouldn’t say the majority of people on Twitter are looking to buy something - they often don’t want adverts for your products shoved in their face every hour & most posts are very short lived.
Pinterest is a big one now too- though this has it’s limitations- the majority of people who use this are women, in fact its biggest draw is women who’re getting married. Though while it has a huge amount of buying power- particularly in the U.S, a lot of UK users simply use it for ideas to then create their own things- though the buying power in the UK is increasing.
Granted there are plenty more social networks for free advertising but I don’t use the others so don’t know a lot about them.
It is a tricky one- I guess your first question is; are you making for a set audience (even if you aren’t a fan of what it is) or are you just making what you like regardless?
Apologies for the long reply- I found myself thinking as I was typing… 
