Good luck.
I did it 25 years ago and would never go back. The most important things I have found to watch out for are :
It is just as important to be a thorough at the buisness side as it is to be thorough a the electrical bit.
If the deal doesn't sound right, look right or smell right, it usually isn't. Walk away, or at least double or triple your price to make it worth the grief .
Don't under-sell yourself just to win work. It's really depressing to have to work extra hard knowing you are losing money whilst doing it, and you can't sustain it for very long.
Sell yourself on how good you are and the value you offer, not on how cheap you are. It's much harder moving up market than down market, so don't start off in the gutter. Someone will always under-cut you no matter what your price. As long as you are not in cloud cuckoo land you will get the work you really want because the client wants you, not the other guy. What would you pay for a set of VDE screwdrivers £1.99, £19.99 or £99.99? I bet you would pay over £30.00 if you liked the look of them. If the client is determined to get the absolute lowest price, let someone else do it. Don't allow yourself to be drawn into a Dutch auction. He will probably complain at the end of the job anyhow.
Do the sums before you quote. Don't forget to include costs for your van, busness insurance, advertising, tax, office materials, subs etc.
Cash is king and declare every penny you earn with pride. We all know someone who has fallen foul of the tax man. If you can't do it legit, you won't last long and you will never sleep soundly. The taxman's bite is much worse than his bark.
I find that not asking for a deposit but insisting on full payment on completion works best for domestic jobs.
If you are a subbie for another contractor, remember you are just a tool to him. He has plenty of others in his tool box and if it's in his interests to abuse one, he will. If he misses one interim payment and won't write a cheque then and there, he is either suffering cash flow problems or has no intention of ever paying. Either way, the longer you stay on site, the less likely you are to see any money.
Be very wary of Ltd companies, particularly in the current climate. You have virtually no recourse if they go under, either by misfortune or on purpose. The owner can walk away from all his company's debts almost totally unscathed and start up again with a clean slate the next day, leaving you and everyone else the company owes out to dry.
Cash-flow is the usual killer. Watch what you spend as eagerly as what you collect.
There are very few that never advertise. Look at how many adverts there are in your local yellow pages. Big adverts are not always big companies. Spend your advertising budget where everyone else does and ignore all the telesales calls.
Spread your self around. 10 small clients is better than 1 big one.