Blue Bell--I use 1/4" seam allowance. Sometimes I trim to 1/8th; sometimes trim just one seam allowance; more likely don't trim at all. Some tips:
1. I like a little starch on the fabric (I usually prewash my fabric).
2. Use Creative Grids rulers--they have very narrow black lines and a non slip backing to assure accurate cutting.
3. Use my 1/4" foot to assure accurate sewing.
4. One of thing to avoid is what I call the "lr swing". Sometimes we like to start too far to the left, then swing slightly to 1/4" and then swing too far to the right at the end of the seam. This really throws matching those seams on tiny pieces off.
5. I always press to one side when sewing a block.
6. If I have sewn rows of blocks I will press those seams open.
7. A small tack hammer really presses intersections flat--now where did the grands put mine?