You'll need crampons on Lion's Head, maybe not on Boott Spur. If you're just going to the bowl to watch skiers and not pushing for the summit, good waterproof boots will do it and a pole (or 2), as Bill says. If you postpone until June or July the blackflies'll eat ya alive, until you get above treeline. I like to hike in September the best, but you have to be real careful about the weather, as you do all year, but theres no flies.
KDT