I have been trying to make it in the crafting business for 5 years now. It is a very difficult business to get into. There are some tips I have picked up through trial and error that may help you along the way.
You will not become a millionaire in the crafting business but you can make a pretty profit if you plan things correctly.
You need to: set up and stick to a budget calculate the time you put into each item shop around for supplies for the best price and research things that are selling around you
A good example is the Red Hat Society. Crafters around the U.S. tried to cash in on red and purple craft items that would appeal to this exclusive group of women. So it's important to know what things are hot each season.
You will also want to buy ahead of time in order to save money. When Feb 15th comes around, hit all the stores you can think of to pick up items you can use for Valentine crafts for next year. This will save you a lot of money and give you ideas for the year ahead.
Sign up for a few little craft shows and get your feet wet before you dive into one of the big ones. You'll need experience with all kinds of different customers and shows to be prepared for bigger shows and fairs. You'll need to learn how much product you'll need to fill your booths, what things sell well, and what kinds of displays seem appealing to your customer base.
There will be shows that don't go well and there will be shows that you sell almost everything you've brought (though rare). Don't let a poor turnout discourage you. Cater to your "audience" to make the best profit. 20 dollar ornaments will probably not sell well at a hometown craft bazaar. They would do better at a larger Christmas themed fair (but there is a bigger entrance fee associated with these).
I've made a nice profit for myself making craft items on the side. I could have never made a living doing it though. If you plan to do crafts exclusively, work up to it. Don't quit your day job right away. Spend a few weekends making some "fun money" to get a taste for the whole thing.