Which consulting firms pay the best?

Does anybody know which IT consulting firm pays its consultants the most? What percentage of bill rate do they pay??

There is no right answer to this.. Each firm and each agent and each client and each contract will have different rates. As a new consultant to a firm they tend to have a higher margin but once you are established with a firm the margins drop to ~15-20% for short term, 10-15% for long term.
 
Here are my tips.

• Determine what your rate is and tell the Headhunters that what you want.
  • Make sure that it is no too low.
  • Make sure that you include within your rate all costs for example: Training, PC, internet, exams, holidays.
  • Tell each headhunter that you want to know the margin that they are charging.
  • Avoid any company or headhunter that will not tell you their margin. They will be nothing but trouble.
  • Get certified! This help increase your rate.
  • Determine if you want longer projects or short term projects. Short term means higher rates but potentially more downtime. Long term me, much lower rates.

Keep in mind as well that pay often varies based on geographic location, especially if you would be primarily isolated to a particular region.  So it's apples and oranges to compare a consulting position based out of Cleveland to a position based out of New York City.