I've been self-employed now for the last 4 years, so i'm not as experienced as others here and i'm in a totally different industry (web development), but they are both service industries, so some of my advice might be useful.
No.1 Do a business and marketing plan - this is the most important. With it you can work out a 2 year projection of your finances, this will determine what your outgoings will be including: marketing, insurance, travel, bills and of course your wages! Once you work that out you can then add a figure of how much money you realistically would like to earn. Add that figure to your outgoings and divide by a number of jobs you expect to do, this will give you an indication of what you need to charge for each job.
The other way to do that is work out how many hours you'll be working and divide the figure by the hours, this is your hourly rate.
No.2 Get an accountant, and a good filling system, you can do the tax-returns yourself, but each time i've got my accountant to do it for me he has saved me more money than what he charges, for instance one year he saved me £2000, and his charge for that was just £350.
No.3 Get decent business cards, flyers and maybe even a website (and at the very least an email address), make it as professional as you can, when you complete a job, ask the customer for a testimonial - you can then use this on any marketing literature.
No.4 Do not haggle on price - ever! Customers who are too cheap to pay the going price often and nearly always become nightmares and these are the customers who usually fail to pay.
No.5 Have a very clear payment policy and maybe even have a lawyer to draught one for you so that you can give this to the customer - this is both professional on your part, and protects both yourself and the customer, so everyone is clear on how the payment is to be made and within what specified time.
Save 30% of every job as a 'quiet' fund for when things slow down - and that will happen at some stage.
Save 25% for your end of year tax, it's a real pain when you come to pay your tax and you havn't put enough away, stick it in an ISA or high interest account and earn some interest on your tax money ;-)
I could go on and on, but I think my most important tip is: Don't work too much, don't be afraid to turn down a job to spend some time relaxing, with the family etc.. If you work too much you'll lose passion and end up in a black tunnel, i did this in my first couple of years, and was totally unessary and depressing.
Good Luck, hope this wasn't too long and boring.