How do you manage your keys?

One thing storage unit buyers have a lot of are pad locks. With multiple padlocks comes multiple keys. That being said, how do you keep track of which locks and keys go together?

You could color code them, or do what I did and order a lot of them all keyed alike. One key fits all! 

I always have a dozen of them on me. I superglue a small piece of plastic on each key and lock and have the corresponding numbers on each. Easy peasy