Your quiltmaking skills will improve immediately when you learn how to press quilt blocks. Pressing seam allowances as you work helps eliminate little bits of fabric that become "lost" within seam allowances, creating distortions and making your finished quilt blocks smaller than they should be.
Additionally, careful pressing saves time because your quilt blocks will fit together exactly as they should when it's time to assemble the quilt. Let's say your quilt block contains a row of pieced units with a total of 10 seam allowances in the row. What if a pencil line-width of fabric is caught up in each seam allowance simply because you didn't press? It doesn't sound like much, but multiply that line by 10, and it becomes the difference between stitching an accurate quilt block or a block that won't match up to its neighbors. You've perfected your quarter-inch seam allowance, so don't allow inadequate pressing to destroy your work.
Press, Don't Iron
Allow the heat and weight of the iron to do the pressing. Avoid moving the iron back and forth vigorously across the surface of your quilt blocks because the movement will probably stretch them out of shape.
You can use more movement when pressing large pieces of fabric, and sometimes it's necessary to work into a seam allowance with the tip or side of the iron but take care not to pull and tug with too much enthusiasm.
Quilters disagree on whether or not to steam-press. It could contribute to stretch, but sometimes steam is helpful.
Can help you square-up a skewed block
Produces crisply pressed seam allowances and fabrics
Tugging at a block that's been dampened with steam could make it stretch
Could cause some fabrics to bleed, leaving stains
Keep a spritzer bottle filled with water on the ironing board. If you need a little moisture, spray mist a specific area to avoid sending loads of hot steam throughout my quilt blocks. Try pressing your quilt components and blocks with and without steam to find out which method works best for different situations.
Step-by-Step Pressing Process
Turn Iron to Cotton Setting
Turn your iron to the "cotton" setting if pressing cotton patches.
Place Patchwork Down
Place the patchwork on your ironing board, unopened, just as it was sewn. The fabric that the seam allowance will be pressed toward should be facing up. Most quilting patterns tell you which way to press seam allowances.
Set the Seam
Set the iron down on top of the unopened unit to set the seam.
Flip Fabric Back
Let the unit cool a bit, and then flip the top fabric back gently, using your fingers to fold it away from the bottom fabric along the seam line.
Press Seam Flat
Place the edge of the iron on the lower strip and very gently work it toward and over the seam allowance. Excess pushing and tugging can stretch the fabric, so take care. Allow the heat and weight of the iron to press the seam flat. Raise and lower the iron along the entire length of the seam to finish pressing.
Press From the Back
Turn the unit over and press from the back to complete the job.
Remove excess strings as you work.
Inspect the unit from the front. Notice that seam allowances on the back make the front of the unit pooch out a bit, creating lofts that butt into each other for a snug fit when it's time to sew units together.
Sew Quilt Block Components Into Rows
Sew units together to create rows, and then press seams in each row as directed in your pattern. Then, sew rows together and press the completed quilt block.
If your quilt pattern doesn't specify which direction to press, try to press seams that adjoin each other in opposite directions.