http://www.checkbook-covers.org
I feel that the first step toward being on top of your finances is starting a budget. This allows you to be able to closely examine how much money you have coming in, and how much is going out.
I used to be one who never worked out a budget. I didn't keep track of my expenditures in a checkbook register or log. I just spent what I thought I could spend on what I would want, without thinking too much in detail about how this related to my income.
It was like use the credit card here, use the debit card there, and then when the bills would come in, I would scratch my head and think how did all that get there!
This is what got me into credit card debt in the past. I didn't keep close track of my expenses, and when my direct deposit pay stubs would come in (I worked hourly at the time), I would just throw them on the mail pile, without tracking the exact amounts to see how much came in for the two weeks.
So basically, I was operating on a system of guesswork.