Never ever bill by the hour. It's inherently unethical, and you're leaving money on the table. I've written extensively on the rationale, which I won't post here, but you can read it here.
I’ve found the biggest problem a consultant will encounter is a client who is unable to articulate value. You have to help the client understand the difference it will make to them and their business if their problem is solved/removed. Only then can they explain it to you so you can understand it.
Hourly billing isn’t transparent, it’s unethical. The longer the client waits, the richer the consultant gets (if you consider a couple of hundred bucks “riches”). If you want to be a commodity, bill by the hour and suffer price competition. If you want to be a consultant, bill according to the value of the results you help generate. Helping a client in five minutes is far more valuable than five weeks, so why not believe in yourself and charge for your talent not your time? I’m outta here!