I have had the following suggestions from other people. The sum of which seem to work ok.
1) Baby oil. Seriously, it makes short work of road tar.
2) Use that liquid spray-on way by Turtle Wax that used to be called (and I guess it still is) Minute Wax.
3) 3M Adhesive remover.
4) Normal everyday FLAPS Bug and Tar remover. Pick your favorite brand. I don't like these as much as some of the home brew methods because of the brands I've tried, they seem to be VERY watery and as such, tend to let your sponge/towell scratch paint more easily. That's just my opinion so take it for what you paid for it.
Personally I've had the best luck with #2 for bugs.
Rick