DH and I have just set up a business, and touch wood it's going well so far. The biggest piece of advice that I can give to you is make sure that you do your research, you don't say what you are thinking of doing but we have a card, party and gift shop, we had to find somewhere for it where there wasn't a Clintons etc. Luckily the village that we are in has it in the lease contract that we are the only shop of our kind in the village and that nobody else can come in and do the same as us. Make sure that you know the market that you are going into, if not ask, ask, ask, ask! We went to a lot of retailers with similar businesses in the weeks that we were setting up to get advice and help from them, and most were very helpful to us.
I know others have recommended Business Link, but to be perfectly honest they were useless for us, and did nothing but try to talk us out of what we wanted to do!
Don't expect to make a million in your first week either, we have days now where I wonder what we have done, then other days it's great, you have to be prepared to take the rough with the smooth.
Its a LOT of hard work, DH and I work 11 hour days in the shop and then when we get home (usually at about 8pm) we eat and go to bed. Bear in mind that we have two small children too! We are bushed most of the time too!
It will affect your holidays and spare time too, so be prepared for that, DH and I have had to plan our WDW holiday for Christmas and DH's mom is being kind enough to run the shop for us while we are away.
This sounds like doom and gloom when I read it back, but it's not trust me! We are having fun and not havng to answer to a boss is great. It is hard but I am hoping that we will be able to take on a (trusted) member of staff next year to help and we will get more time to ourselves then ( and maybe look to open another shop!)
HTH
Gems