I've been doing this for 15+ years.

My thoughts (UK specific)
1. Get a good small business accountant. They won't cost much, will keep you out of trouble and will tell you about tax allowances etc (did you know you can claim a portion of your domestic fuel and lighting if you are working from home?)

2. Keep all your business receipts and maintain a simple cash flow spreadsheet or cash book. Reconcile it to your bank account every month.

3. Network like mad. Build an interesting one or two line description of what you do so you can tell people clearly and succinctly. Go to networking events and meetings, get people's business cards, and follow up with a call or an e-mail.

4. If you can, keep an office area distinct from the rest of your home. Get up and 'go to work' very clearly. On the days where its just not going well, or no-one is available to talk to you, make a positive decision to go out and get fresh air ('if you're going to goof off, goof off positively')

5. There is quite a lot of help and quite a few grants for people starting new businesses in the UK. Go to your local Regional Development Agency, your Local Learning and Skills Councils, Business Link to see what's on offer.

6. Contrary to popular legend, I've always found the tax and VAT people quite helpful when you go to them with a genuine issue or question.

7. Take plenty of exercise, keep fit and look fit. You have to sell yourself over and over again, and people make fairly instant judgements about you almost the minute you walk in the door to make your pitch.

8. Unless you really need a laptop, get a decent desktop computer and screen, and a comfortable chair. You can't afford to get backache. In addition desktops tend to last longer (you don't drop them) - I've only just bought my 4th (Mac) desktop since 1992.

Best of Luck
KP