SmoothOperator,
Before you freak out, understand that what mrblue92 posted is not really average - most people spend more than 25% of their monthly income on rent/mortguage - some even spend over 50%!
There really is no secret to budgeting, and most people avoid it because they don’t like being brutally honest with themselves.
All you need to do is look at your bill stubs for the last 3 months, and work out an average for each one. Cable cost X, Rent was Y, Electricity was Z, etc, etc, etc.
List those costs, add 5% just in case, then compare those numbers to your paycheck. As long as there is something left, you are doing better than almost 75% of your contrymen!
Since you seem to be making a clean break, this might be a good chance to take charge of your finances and create a clean start - if so, let me recoment two tools:
[ul]
[li]Quicken - if you don’t have this program, buy it and use it! It simply takes care of things so you don’t have to worry about them. I use Quicken to let me know if I am sticking to my budget (it helped me make it), write checks (I pay my bills electronically), balance my checkbook (I don’t enter checks anywhere! I just download them each week from the bank), etc, etc, etc. I can’t stress enough how great a product this is.[/li][li]Making the Most of Your Money by Jane Bryant Quinn. This book is an investment ($25.00) in yourself. She covers everything from budgeting to wills to insurance to investments to disaster planning. It’s fantastic.[/li][/ul]
I just re-read my post and I sound like some finance guru - Please understand. I was an English major and can’t add 5 numbers in my head. I am awful with money and used to forget to pay bills all the time.
Until I got into the habit of using Quicken.
Then, things were good, but we weren’t saving any money.
Then I read Quinn’s book!
Now we save money, I am insured so my family is protected, we invest towards our retirement and our children’s educations, etc, etc, etc.
We even have moeny left to rent some movies now and then, though they are free at the library, so we go there more often. 
I hope this was helpful - I certainly didn’t mean to nag. Good luck!