You could always try driving more defensively so as to avoid those pesky bugs. Kidding aside, 3M adhesive remover works real well but it removes any traces of wax and polish you may have so a fresh coat is in order upon completion. I've hit a few this year large enough that it sounded like a rock hitting the windshield.

 

WD 40 will remove bugs, tar, gum, just about anything. After use clean off with soap and water.