Plug for Brennan's plug: This book is amazing. I've increased rates by +$30/hr with the advice in this book. If you send invoices to clients BUY THIS BOOK.
Not to be a wet blanket, but I recently increased my hourly rate by $50 and I didn't need to read a book. I just decided to bump up my rates. And I did.
If you provide value, and you're good at what you do, why not ask? If it's because you can't handle being told no once in awhile, maybe Rejection Therapy[1] is the best way to go. The game can be applied to all aspects of life, not just getting higher hourly rates.
