there's been a lot of discussion of quilt-as-you-go under several topics on this board. search the board (1st thing on the menu at top) for "quilt as you go" and "quilting in sections". it'll make it easier to find the topics and read all the comments and suggestions. there are some links to good instructions, too.
i usually use one of two methods
-sew the blocks together at the back, then decorate the top with sashing to hide the "gaps"
-sash the back and the front to cover and decorate all the seams and gaps.
you'll find many more ideas as you sift your way through all the posts.