Most personal sites use less than 4 GB of bandwidth per month - so keep that in mind when looking at plans. You'll want to choose a host that has larger plans so you can upgrade when needed; but you won't need to start out with the highest-bandwidth plan you can find.
As to which host to choose...that's not a small question. What you want to keep in mind is that you want to not pay a huge amount of money, but that you don't want to go with a host that crowds their servers so extremely that your client's web site runs slowly. You're buying a virtual service, so make sure you know how you'll communicate with the host. Look for a host that communicates well - and your own definition of "well" may mean a host that answers all of your questions no matter how basic, and has IM and phone support. It could equally mean a host who offers support only via support tickets, client forums, or email. It all depends on your preferred forms of communication. (Personally, I get twitchy if there isn't some kind of support forum at any of my providers. I may lurk more than participate; but I really value having that resource there. Sometimes other clients may have insight or ideas that the host's support staff may not have. Other people really very much prefer phone support. It's all down to how each individual communicates.)
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