Not too snug to give you a headache, but it can't be sliding around. You won't have any free hands to move it back into place. The helmet should be low profile. You can get your body into pretty tight places on the rock. You don't want your helmet to be in the way.
Air vents are a nice option for the summer.
And if you plan to climb in the winter, you'll want to find a helmet that will adjust so you can wear a fleece cap underneath. Remember that the helmet won't protect you unless you wear it. You should wear it when you're belaying as well as climbing. Standing below the wall you become a prime target for falling rocks. Blue Water 209 Lovvorn Road Carrollton, GA 30117, USA Tel.