Here is a list of things you can do for a nicer finished product...
Press seams flat.
Remove all stray threads. Yes, they do show through the front!
Make sure the backing is squared up.That means the top and bottom should be parallel to each other. See diagram below.
Save trimming your borders (especially curved ones) for after the quilting process. It's easier to load a straight edge.
Remove all interior selvages, including those on the backing. Selvages on the outside edges don't matter since they will be removed prior to binding.
Make sure the backing and batting are 4" larger all the way around.
Backing seams should run side to side, if possible. Vertical seams are manageable but may create an uneven pull.
Pre-wash the backing if you pre-washed the quilt top fabrics. Backing and quilt top laundering history should match. Wash them both, or don't. It's that simple.
Batiks should be pre-washed 2-3 times prior to quilting. The weave is very dense and can cause thread breakage during the quilting process. However, the "wide backing" batiks are manufactured with a looser weave so the pre-wash on these isn't necessary for quilting purposes.