When this quilt was finished I had only a Ziploc sandwich bag full of leftovers.
My second strategy is to use up leftover yardage from the quilt front. Here I bought a yard of Menagerie on sale and fussy cut only a few squares for the front, so I had a lot of yardage leftover. I used more of the focus fabric for the back than the front.
My favorite method is to piece the back using strips. With baby quilts this is super easy. I just cut width-of-fabric (45") strips and piece them together. My baby quilts are usually 36" wide so this works well - I like to have the back be a few inches bigger than the front on all sides.
However piecing strips is only easy if you make them big. If you make the strips small and you do straight-line quilting, it can be a pain to make sure your quilting lines up with both the front and the back. This quilt took a LOT of basting pins.
The final strategy I use is solid yardage for the back. Even here I try to use a few scraps, with prairie points in the lower right side.
What are your strategies for piecing quilt backs?