The very first quilt I made I did not prewash. The dark red color (which my "teacher" helped me choose w/o any warning!) I'd used on the border bled into everything. I ended up discovering the little sheets you can put into your washing machine (color grabbers) and they took out the extra color. But the thought of giving a quilt to someone and having them go through the trauma I did because the colors run terribly is not a nice thought.
I use a plastic tub in the kitchen sink and keep HOT water in it with the fabric for 20 minutes or so, squeeze what water I can out (no twisting) and then put it into a HOT dryer just until it is done, or almost done. My dryer has a cool down cycle and I put the fabric in for about 10 minutes before that cycle and if I get them out right away they are smooth and wrinkle free. If it turns out wrinkled you let it get too dry.
I've seen a lot of my quilts that my kids and grandkids have used and they are all soft and cozy looking so I don't think the "let it shrink to look like quilts of old" is as valid as some would like to think.