Well the first meeting is really to get to know each other. Assume you have finished the prep course? I am a retired sw and manager (30 years experience) I would always just have a general chat and cast my eye over the house (don't mean looking for everything spick and span - far from it) but just to make sure it is reasonably clean and you can tell this immediately. I think the process of the assessment should be explained to you on this visit, and sws sometimes forget to do this, and rush on with the paperwork.
The F1 form is just to collect factual information about you and your family, names, address, dates of birth, may want details of your education and working history (for both of you) how long you have lived in your present house, etc etc. I would always ask if the aplicants are in good health and also if there were any offences as it would be best to know right away, as the sw has to apply for a CRB police check.
I think though that if you are wondering about something, just ask.....sws are ordinary mortals you know! Sometimes they forget that something they are doing on a regular basis will not be known by applicants. She/he should should tell you how often they will visit to carry out the F2 which is the comprehensive assessment (might be called something different now!) you can't be exact about this because all assessments are different. The sw may ask you for names and addresses of referees they can approach.
So relax - offer a coffee and suss the sw out as well as you need to be able to work together in an atmosphere of trust and harmony, but of course sws like everyone else differ, so hope you get a good one. Oh just thought sw has to complete a Health & Safety check on your home, so if I saw anything obvious on my first visit (like an open stair case) if it is young children you are considering. Mind having said that I think if there are big alterations to be made, it is not fair that the applicant starts making changes until they have been approved.
Sorry I might be overwhelming you with info...............am sure it will be fine.