Here is the method I use when designing a new pattern for doll clothes. It helps if you already have a good understanding of what clothing patterns look like. If you are a beginning doll tailor, I recommend using the patterns that are available here at the Doll Making Site, or buy commercial patterns, until you are more familiar with doll clothing construction.
When I set out to create a new outfit for one of my dolls, creating the pattern comes first. The easiest way I've found is to lay a few sheets of computer or copier paper out on my cutting table. Some designers like to use tissue paper, like commercial patterns are made of. If this method works for you, great, but I find it is too fragile and tends to tear to easily. My fingers can be quite clumsy!
I like having the paper on my cutting table because the inch markings are already on the table and it's very easy to see the lines through the paper, so I know my lines are straight when I need them to be. I tend to be a free hand designer so having the lines there simplifies the process for me.
Use a tape measure on your doll and take a thorough set of measurements for what ever body part you are making clothes for. Be sure you include the measurement around the arms and legs. This gives you a starting point for how wide pattern pieces for sleeves and pant legs need to be. Then add in seam allowances and enough width to allow the clothes to move easily on the doll, as well as putting the clothes on the doll. It's always surprising to me when I see how wide the pattern pieces need to be. It also helps to have the unclothed doll on the paper so that you know how long the clothes need to be.
Once you have a pattern piece that you think might work, wrap it around the doll, the way the clothing will go and see if it fits. Once you have a pattern that seems to work, trace it again onto a clean piece of paper. By the time I get a pattern piece that seems workable, I've erased and redrawn so much that the paper is messy and confusing, a neat pattern saves mistakes in the cutting.
Always try out your pattern on old or scrap fabric. Designing your own patterns is a process of trial and error, it's always better to save the good fabric for after all the bugs are worked out.
Skirts are quite simple to design. Just measure the width around the waist of the doll and multiply by 2.5, add in the seam allowances, and this is how long the fabric needs to be. Decide how long you want the skirt to be and that becomes the width of your piece of fabric. A simple rectangle is all that's needed for a skirt.
Designing your own doll clothes patterns can be lots of fun and gives a real sense of accomplishment and pride.
Making and Dressing Cloth Dolls
Ebook with patterns and instructions to make 5 cloth dolls as well as chapters on general doll making techniques.The book includes 21 inch Lalena Doll, 21 inch David Doll, Bear Dolls, 9 inch Destiny Doll and 15 inch Annie Doll, all together in one handy book. 53 pages.Making and Dressing Cloth Dolls.