installing children's seats

Anybody have any good ways to install children's seats? I have a 95 burb, and it doesn't have locking retractors on the seat belts. I've tried using a locking clip, but it doesn't seem to hold the seat tight as the buckle gets in the way and ends up leaving too much play in the seat. Is there a way to turn the locking retractors on that I just don't know about? I've looked in the book, but it really doesn't say anything. I've also tried pulling the seat belt out all the way to try to engage the locking retractors, but that doesn't work either. Does this year of suburban just not have locking retractors in the back seats? The front seats lock if you pull the belt out all the way. Any helpful ideas would be greatly appreciated. Thanks.