I use what many call ranger bands for strap management. They are basically pieces of bicycle inner tube cut about 1/2 inch to 1 inch wide. A GOOGLE search on ranger bands will give you lots of examples and pictures. I made my own from old inner tubes I got from my local bicycle repair store. They GAVE me a bunch of old punctured inner tubes that they replaced. Just make sure to get the small ones, you want them to be a little bit wider than your straps when pressed flat. Otherwise they won't snug down on the straps enough.
Slip them down the strap and then you can fold over the excess and tuck it under the ranger band. For those familiar with the old ALICE packs they work the same way as the elastic loops it had on its straps.