When I SITD wherever possible (on edges of the quilt) I lock my stitches and then snip the threads. On my machine that means a few stitches forward followed by a few stitches backward. If you did not do this and you have thread tails everywhere you could do what I did with my first quilt. Working on the back and back only tug on the thread gently and pull its mate (the top thread) to the back. Tie a double knot and snip the threads so you have small tails left, less than 1/4". These knots will be on the back and nobody will know they are there. Good luck and keep on quilting!