cant add much to deliajen's comments.
Unless you have the money to start big, go with what you know or you WILL throw money away. In the start (year ago) I bought so many domains that I still own and unable to shift that also havent made the £6 reg. fee.
Buy a domain about your hobbies, work, gaming, etc. and go from there. Until you know what to expect, keep away from numbers within a domain.