You’ll want to decide carefully when you should use your Hero Power, because it multiplies your score while it’s active. First, you should let it build up—although keep in mind that you can only have so much at a time. Next, wait until you’ve reached your max multiplier of 4x. Using Hero Power during a 4x multiplier will boost it to 8x. Finally, if possible, use your Hero Power when there are a lot of notes to hit, so you can get as many boosted points as possible.