I would take everyones advice here and keep your hands up at ALL times. Don't get into the habit of blocking too much with your hands, blocking with your hands is okay, but then your hands go down and you don't have full gaurd. Try to block the kicks with your legs instead. For example, if someone throws a side kick or a thai kick, lift the knee up in the direction the kick is coming at you, then that can set you up for a back hand strike or whatever techniques you prefer. You can also intercept the kicks, if someone kicks at you with lets say a front kick, you bend the leg very quicky with the knee pointed down, meanwhile at the same time step down so that the point of the knee goes into the kick, you can do this very quickly, and if done right you can even damage the leg. You can also intercept the kick, kick-the-kick, or not even block at all, just dodge. These are ofcourse things I recommend, only my opinion.