Your own voice is your most important piece of equipment. If you're new to the voice-acting world, look around to see if there are classes or coaching in your area. Outside of class, practice speaking clearly and confidently. Learn to do this even with material you've never seen before. It's also important to learn voice care – straining or injuring your voice can hurt you and your career.
Always update yourself on industry standard rates. I recommend reviewing the union rates set forth by SAG-AFTRA. Voices.com also offers a rate card as well Voice-Over Resource Guide. Upon viewing these rates you may find, based on your current experience, you fall a little lower or higher than said rates. Maybe you have a great deal of experience in the commercial voice-over world, but now you’re branching out into narration, e-learning or audiobooks, so your voice-over rates may be a bit lower for that genre as you find your footing. The most important thing is that you have a baseline rate for yourself and you’re comfortable and confident stating this rate to a client. It’s beneficial to first ask your client’s budget and proceed from there. While stating your rate, also take into consideration edits and pick-ups. It’s customary to include one free round of edits in your rate, but any edits or pick-ups past that incur a fee.