Best bet is keep your skin covered with light weight long sleeves and pants but if you prefer to have skin exposed, do your homework on natural or chemical type bug sprays. Bugs in the White Mountains are unavoidable during the warmer months so there is no real way to keep away from them completely. Above tree line, so long as there is wind, they are kept down, but if you hike on a calm day, bugs will be around from base to summit. And if you keep an eye on forums, you can avoid the peak of the Black Fly period, which will bite you no matter what spray you use. The only other option to avoid bugs is to hike during the cold seasons, but that raises a whole other set of needs and concerns...
Best of luck!
Staff Meteorologist/Night Observer, KMWN (Mt Washington Obs., NH)