Turnarounds can be used as cool attention-grabbing intros to a song. Just start the intro from the shifting melody line in bar 11 and the rest of the band can kick in wherever feels good in bar 12 or at the start of bar 1.
Just the same as intros, a good turnaround is an ideal way to end a song. You need to make sure the song is properly resolved by finishing strongly on the I chord. You also may need to tweak the timing a little as some songs gradually slow down over the last bar or so which can be tricky at first.
There are numerous ways to finish up but the most common is to start a turnaround, hit a staccato I chord on beat 1 of bar 12, and then signal the end by playing a #I chord – I chord sequence instead of the V chord as follows:
Try this ending by playing a bI chord – I chord (Ab7 – A7) instead of the #I chord – I chord (Bb7 – A7) as shown. Notice how this changes the ending from a bluesy feeling to more of an upbeat happy feeling.