1 Start with the best pattern size for your measurements.
Take your measurements periodically just to be sure. Note that the bust measurement on the picture below may be better taken as the "high bust" - meaning across the back, underarms and above the bust. I actually take my bust measurement because fitting the upper body isn't usually an issue. Many women prefer to take the high bust measurement because then the shoulders fit well and then make an adjustment to the bust if needed.
2. Trace your pattern!
If you are going to alter the pattern, keep the original in good condition. That way, if you make a mistake or if you change sizes later, you can still use the pattern. I trace using the 100ft roll of kids' craft paper at Ikea(It sells for $5). It is high quality paper and I use it for tons of things (gift wrap in a pinch; lining cupboards, floor paper when I paint, etc). If you are hard-headed, like me, you may have to ruin a pattern or two before you abide by this sage advice!
3. Tissue fit (or make a muslin...)
This is the lazy woman's way to avoid a muslin. I tissue fit the pattern to my body as a rough guide to whether I will fit the pattern. I don't bother pinning darts or pleats (as these can be played with when putting them in). All I am looking for is whether the fabric I cut will fit my body. I haven;t used Swedish tracing paper, although many people have told me this is fabulous paper to trace the paper on and then use as a muslin. It is on my Christmas list though!!!
3a. Size up with Grid paper
I use graph paper to add to a pattern. Then I simply count squares and add equally to both sides, should the paper pattern need to be enlarged in spots. Graph paper keeps the calculations to a minimum and it is easy to tape the same number of squares to each side.
3b. If the pattern isn't in your size, measure the distance between sizes that are on the pattern and use a multiple of that measurement to make the pattern bigger.
I learned this one from a Burda magazine tip. It is so smart. And it is time consuming. But a few times, I've fallen in love with a pattern that is too small. And so, with some work, I can re-draw the pattern to fit me simply - remember to measure each part of the pattern piece for the difference in sizes to ensure that the shape is not "lost" in the process.
4. I cut with wider seam allowances, especially when sewing pants.
I learned this trick from reading Pants that Fit, and it is a godsend. The trick is to mark the seam lines so that the shape of your garment isn't hopelessly lost in the extra seam allowance.
I'd love to hear any tips you can add to this list. My goal this fall is to fit each pattern I make, so that it works on me!