Lots of good suggestions so far, all of which will help. However, as already said, you'll never do away with this completely. Is the nature of the beast when towing a large trailer with long, flat sides.
I would put the things you can do to help this, in this order. First ones being the most effective (and most expensive):
1. Get a Hensley or Propride hitch
2. Install air tabs on back of the trailer.
3. Leave as much space as you can between you and the big trucks
4. Speed up some, so speed difference isn't as much
