Press all the seams flat (you can press to the side or open, whichever you prefer)
Trim all thread ends
Prepare your backing:
The backing needs to be 10" bigger than your top in each direction. For example, if your top is 50" x 60", your backing must be 60" x 70" (larger is ok, smaller is not).
If piecing your backing, do not leave the fabric selvage in your seam allowance.
Press all seams flat (either to the side or open, whichever you prefer)