No Tucking Area
If your sofa doesn't have creases in between the sofa arm and the back cushions, simply make neat pleats, and tuck all excess fabric under the seat cushions.
If your sofa's arms are thin, wrap them in batting, then cover with the slipcover.
Lay down a nonskid rug pad to reduce slipping and sliding.
Use a wooden spoon or spatula to help tuck in excess fabric. To keep it tucked in, roll up some old magazines with a rubber band and push them into the crevices.
Throw the slipcover in your dryer on a low setting with a damp towel for a few minutes. Put the slipcover back on your furniture while it's still warm to keep wrinkles from reappearing.
Dark colors, bold patterns & piping
Add a light-colored sheet between bold patterns and a light-colored slipcover to prevent the pattern from showing through. If you have bulky piping, you can add batting to keep the surface flat and even.