One of the easiest ways to make a few dollars with your crafts is to be a vendor at a craft fair. Many local churches, firehouses, and schools have seasonal craft shows. The most popular time of year is around the holidays and in the fall. Look for flyers, newspaper advertisements, and roadside signs to let you know when they are having them.
Email the event organizer or call the number they have posted. Let them know you're interested in reserving a spot to sell some of your crafts. They'll charge you a nominal fee for your spot (this is how they make money on the event), and from my experience it usually runs $10 to $25 for a spot. Some of the larger venues can cost you more, it just depends on the size and popularity of the event. You can always ask for two spots, but you'll have to pay for both of them.
Be sure to ask if they supply tables, chairs, and electricity. If you have a computer, credit card terminal, fans, or other devices that need power you don't want to assume it will be available. Sometimes they'll charge for tables, other times they come included with the reservation. If you think you'll be doing this regularly, it doesn't hurt to invest in some tables and comfortable chairs. Most of the chairs you'll be provided with are fold-up wooden or metal chairs, and they're not very comfortable to sit in for hours at a time.
If you're just starting out with your craft business, it's always good to take some flyers and business cards with you. If you have a computer and printer, you can make these items yourself. A lot of times someone at the show will see your crafts and have someone in mind for a birthday or Christmas gift. I've acquired many customers this way, simply by having some business cards sitting out for people to take.
While you're set up at the show, take some time to see how other vendors are displaying and selling their crafts. Many of these people have been doing this for years and they know what works. Don't steal someone's ideas, though. I'm sure if you spent a lot of time and effort on a really nice handcrafted Christmas ornament, you wouldn't want to see your idea at another show.
Usually the sponsors will hold the same craft show each year, so make a note and get some contact information if you want to come back next year.