Press each seam after it has been stitched. Patchworkers usually press both seams to the same side, as it is stronger.
Many teachers tell you to always press “behind the darker fabric” so that there is less chance of it showing through.
Although this is a good general rule, it isn’t usually important with the good-quality fabrics we use today, and it can create lumpy bulk at seam joins, spoiling your chances of a good line up with the next seam.
If your pressing is planned so that seams always meet another pressed in the opposite direction, this makes for much flatter joins, and perfect points – look out for this as a feature in all my patterns.
If you sometimes end up with a small tuck in your seam after pressing, this video shows a good tip on how to avoid this: