Another 'new business' thread

I was out for a walk with the missus and our little one and the thought occurred to us both that it would be awesome to have a babies play cafe in our area. The kind of place where you can go with a little one, sit and have a decent coffee and play with your baby without bothering the kind of curmudgeonly gits who don't want that kind of thing at their local Nero. Coincidentally, we saw a vacant business premises to let, which would be perfect for just such a purpose. This has set me on a chain of thought that I don't want to let go of until I've at least done some proper research to find out if this might be possible. The truth is, that although we've had a nice idea, neither of us have much experience in making a business plan or starting a business from scratch. We are both thinking that there must be an awful lot that we don't know about, which we really should know about if a venture like this is to survive. Things like accounting and the legal aspects of running a business are going to be completely new to me. I actually don't know exactly how much I don't know.

This is why I have decided to approach the BBS - long acknowledged as a comprehensive font of knowledge, good business sense complete lack of sarcasm - to give me some pointers as to what must be borne in mind at the seminal stages of making a startup small business. I'd like to ask for your input as to what I might have forgotten . Considering I'm starting from a very small knowledge base, please don't assume I'm remembering anything that you think should go without saying. The chances are, I don't know about it. Particularly, I'd like to hear from anybody who has learned something in their small business that they wish they had known from the start. Over to you BBS. Show me your pearls. Of wisdom.