I read Joe Frazier's book on boxing training. He is very old school and doesn't recommend lifting. His son Marvis, who is also a trainer now, supports lifting weights. My old coach also supported weightlifting as a suppliment. Currently, I lift once per week, but limit my lifting to benching (flat and incline with bar or dumb), deadlifts with rows (a great compound exercise), dips, and chinups/pullups. Palms-in chinups work the biceps, too, so that's all I do for biceps.