I volunteer regularly & I was wondering what the best way to keep track of volunteer hours is, if u need signatures, the best places to volunteer, etc. Thanks! 
You don’t need to keep track of them. Rather than simply logging hours, focus on accomplishing tangible goals through your volunteering efforts.
Colleges never really ask for an accurate hour count or signed time sheet. I believe the common app asks you to estimate the number of hours per week you dedicate to the activity.
If you really want to keep track though, an excel spreadsheet should do the trick., but as MiscTroll said you should really focus more on doing tangible work than logging hours.
MobileServe is a great app for this
Come December 28th of your senior year as you’re filling out your Common App, you sit down and make a wild guess for 9th, 10th, 11th and 12th grade. That’s about the amount of time you need to spend “tracking” your vol hours. Colleges don’t care if it’s 20 or 500 or 0. really.