The perfect seam allowance is actually a SCANT quarter inch.  This is due mostly to the fold of the cloth over the seam allowances.  In addition, hand sewers use a slightly larger seam allowance than machine sewers, as there is twice as much thread in a machine-sewn seam.

The general rule is to never sew over an unpressed seam.  However, during block construction there is a danger of distorting the bias if seams aren′t carefully pressed.  You may find finger-pressing faster and safer than conventional pressing.  Just turn the seam in the proper direction, and use the heat of your fingers to press the seam.  Just the part of the seam you are about to sew over needs to be pressed, not the entire seam.  Be gentle and do not pull or distort the fabric.  Pin and sew the next section of the block.  After the block is completed, or at least after a section has been completed with no bias sections on the outside, press with an iron in the conventional manner.

Sometimes it is necessary to pin before sewing patchwork.  Do yourself a  favor and use pins with a thin shank.  Thick pins will only be a nuisance and will many times shift the seam.

Value, the relative lightness/darkness of your fabrics, can be more crucial to your quilt design than the actual color of the fabric.  You will find your blocks leap to life if you make a concentrated effort  to combine lights, mediums, and darks into your quilt.   For example, blue and green may be a beautiful color combination, but if you used only blues and greens of the same relative value your quilt will not come to life.  In fact, if may be hard to see the piecing at all!  Why do all that work if no one can see it?

There are several ways to determine the value of your fabrics. 

Try freezer paper for your foundation when paper-piecing.   Iron after each patch, and the fabric will stick temporarily.  No more danger of the fabric pleating or folding while you are sewing the next patch!    But if you do get in a bind and have to rip seams, use Scotch Magic tape to repair your paper foundation as it will not gum up the needle.

One nice way to try out a new pattern is to use Christmas prints for your test block.  After a few years you will have a nice pile of Christmas blocks to incorporate into a sampler.

Whether you are an applique artist or prefer patchwork, try a little starch before cutting your patches. 

Don′t forget to starch both your completed top and backing fabric heavily before machine quilting.   You will find there is much less risk of pleats when free-motion quilting.

Use either bias or cross-grain strips for making binding.   Cross grain strips are cut from selvage to selvage.  Because of the way the fabric is woven on the machine, there is a slight stretch to cross grain strips.  Straight-of-grain (or lengthwise) strips are cut parallel to the selvage. There is very little stretch to the straight-of-grain (lengthwise) strips and it is not appropriate for binding.

You must use bias binding if your quilt has curved edges.

If you did not quilt all the way to the edge, baste the edges of your quilt before binding in order to compress the edges.

Avoid putting seams in the binding in the corner of the quilt.   Before sewing on the binding, pin the binding to the place you are considering starting and quickly lay out the binding along the perimeter to check where the seams are going to hit.

Always sew on your binding with a walking foot.

Consider cutting bias binding 1/8 wider than what you normally cut for cross-grain binding.  The bias seems to stretch and may seem a bit too narrow if you don′t. 

Batting and backing fabric can help stabilize a wall quilt so it will lie flat on the wall without ruffling.  Try orientating your backing fabric so that the lengthwise grain is vertical.  In addition, many battings have a grain.  Test for stretchiness, and put the most stable grain vertically. 

Are your borders ruffling around the edges?  Does your finished quilt top not lie flat?  Is your finished quilt not square?  Try this method!   When sewing on your border strips, NEVER just sew on longer strip and then whack it off at the end!  Many times, the edges of your quilt have stretched.  You must measure through the center of the quilt.  Cut two strips exactly that length (for example, the top and bottom border strips).  Find the center of the strip and the center of the quilt top.  Pin that spot and pin the both ends.  Now carefully pin the entire border, while you distribute the extra fullness evenly.  Disengage your walking foot or even-feed foot.  Put the biggest part next to the feed dogs.  90% of the time the center will be next to the feed dogs, with the border strip on top.  Let the feed dogs do the work to ease in the larger area to the smaller area.  You may have to hold the fabric firmly while sewing if there is a lot of extra fabric to be eased in.  Press. Do the other strip the same way.  Now measure through the center of the quilt the opposite direction and repeat!  No more ruffles!  And your quilt will be perfectly square!