It is hard to remember a time when I didn't know how to create my own patterns. I started pretty young. But lots of people don't have my rather strange range of experiences to draw from and I often get asked how to design clothes. Well, I'll tell you what my pattern drafting teacher told me, 'It's not rocket science.' It might seem difficult, but really it isn't. I swear. To help you get started, here's a few sites with some free tutorials on how to draft your own dolls clothes. Some use some cheaters methods, but heck, why re-invent the wheel if you don't need to, right?
Hereis an extremely basic explanation to get you thinking from Helen B Wharton.
Here is a much more detailed tutorial on how to make a doll dress from Tiny Zippers.
If you've gotta full sized people pattern that you'd like to make doll sized here is a great cheater method from Dale Rae Designs. It looks like you have to buy something here, but scroll down to find the freebie.
And here is a tutorial from Rivkah Rosenfeld on how to design any ol' doll clothes you wanna.
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Now that will just get you started. Remember what is the worst that can happen? You might waste some paper, time and some really small pieces of fabric. No big whoopee. Go for it!