You can do hand streatches, like Kirk Hammett do.
Hold your arm out in front of you, absolutely straight. Then hold your hand straight up and do that live long and prosper thing that Spock does on star trek, and hold that for a while. Then move your middle and ring fingers together in the middle of your hand, and keep you index and pinky away from those fingers, and hold your hand like that for a while.
Now do the same two hand positions only with your hand pointed staight down at the floor. Your hands should be streached out fairly well, and that'll decrease the time it takes for your hands to get going.