There are many sites with this type of information already out there, so I won't try to recreate them here. I would like to say you must advertise. If no one knows you're selling, how will they find you to buy anything?
It doesn't have to be complicated. If you're selling at the big craft fair at the rec centre that's been an annual event for the past 20 years, basic advertising is probably covered. You may want to mention to friends, family and coworkers that you'll be selling there. Ask them to drop by your booth or table. Odds are they'd rather buy from you than from a stranger. Be careful though, they may ask for a discount!
It's a good idea to have contact information on your business cards, order forms and so on. From the advertising point of view, you want to get your name and contact information onto every slip of paper you distribute so customers (and potential customers!) will have a way to reach you.