I worked as a social worker for many years in CT and did homestudies for adoptions and for foster placements. First of all, RELAX! It's not too bad a process, usually, and they really aren't there to judge you or your home, i'm sure you will do fine. Mostly, social workers are looking for the negatives, things that raise a red flag, such unsafe conditions that could cause harm to the kids. Exposed wiring, ungated pools, poorly trained dogs, ect. They also want to get a sense of you and how you will parent, but that's very subjective. As far as cleanliness, we were told repeatedly that we could not fail a home because it was not clean enough (I certainly wanted too some times!) but looking good doesn't hurt. Safety latches and outlet covers are good, but not allways required. The agency you are working with should be able to give you a set of guidelines to help you prepare. A good homestudy is really just a report on how well you meet those guidelines.
I know that when we found someone whom we thought would be a good parent, we looked for ways to pass them on the homestudy, even if thier home was less than perfect. Good parents make up for a lot!