If necessary, until you gain more experience, draw the 1/4" seam line on each piece. Tedious, I know, but when I was a rank beginner, I could not eyeball the seam allowance and 1/4" piecing feet were not available. Also, are you hand piecing these blocks, or are you machine piecing? Pin every little interval to keep those pieces in order and starch if you have to. Use a little piece of fabric to start sewing on (Fons and Porter) and then slide your seam underneath. This helps to guide the small pieces smoothly under the needle and don't forget to use a skewer or pointed tool to guide the pieces under the needle.