I have quite a bit of experience with Estate Agents (and have worked as one myself, ducks to avoid flying rotten eggs) and imho these things are really important:
Bearing in mind that the agent works for the vendor, not the buyer:
Giving honest feedback from the viewer on every viewing. Last house we sold, we had about 10 viewings. We sold quite quickly, but never heard what the others liked/didn't like about the property.
In this hot market, NOT sending round people on viewings who are not in a position to buy. Helps enormously if they have already had mortgage advice. Too many people go out on a Saturday just to "get a feel" for what's available. But it takes a lot of effort for families to have their house tidy enough for a viewing, and fit in around the rest of family life, so only serious buyers should be allowed, without the express permission of the vendor.
Fees are important too. Moving is cripplingly expensive and sometimes you wonder exactly what the Estate Agent has had to do for their £thousands.
Being honest to the vendor about what you could do to improve your chances of selling. Ie. not having dirty undercrackers lying around on the floor etc. Need to be upfront.
At the same time, being honest with the viewers about what the property is actually like - so they don't turn up and are going to be instantly put off by things like - oh I don't know - being near a pub, or on a busy road, or needing a new kitchen, etc etc.
Thats all I can think of for now. Will come back if any more occur to me.
Good luck with your new business - I always loved being an Estate Agent and am thinking of trying to get back into that line of work. But then it really is a young people's game isn't it - what with people expecting you to do accompanied evening viewings and Sunday viewings and everything. Estate Agents aren't ever supposed to have any time off, are they?