This old pamphlet from Marvin J Ashton is classic and still relevant today.
It outlines the basics of using a debt repayment schedule. The recommendation is to pay down the highest interest debt first, then take the money you were paying on that loan and put that money on the next highest interest loan. Keep doing this until all your debts are paid off.
This pamphlet was one of my first introductions to managing finances. The counsel is great, the method is great. I highly recommend it.