Electrical outlets

Have you done electric work before?
Are you comfortable doing electric work?

Do you just want to add on to the existing outlets?
Or do you want to run a new circuit with new outlets?
Where are you located, as codes do vary?

Are the exiting wire runs in conduit or bare wire?
Are the garage walls finished or open?

That depends on how comfortable you are with doing this and how much knowledge you have about electricity. If is a fairly simple project if you know what you are doing. The hardest part would probably be running the new wires. If you don't know what you are doing then it is probably best to call the electrician.

Well, never done any electrical work. Not really comfortable, but I am trying to expand my diy'ing skills. Thought there would be a step-by-step guide to follow.

I guess I could always watch, and learn for future projects, huh.

If you answer some of Dave's questions you may be able to learn how to do this. Even if you don't do it yourself (since you are not comfortable with it) at the very least you can "supervise" the electrician and have questions to ask and make sure the job is done right. Usually when hiring a "professional" if you don't know absolutely nothing about the project you tend to take their word as law and once in a while you will find a "professional" that is not worried about doing the best quality of work. I study up on anything I am hiring a pro to do. Good luck.

It's easier to extend from the last outlet box on the daisy chain as opposed to branch off from a box not at the end.

Having a third cable come out from a box to extend in a different direction may run you into the problem of box fill, having too many different wires inside that box. Box fill should be discussed in any good do-it-yourself guide book.

You can install a GFCI receptacle unit in the first outlet box so as to protect all of the receptacles new and old.