I'd recommend firstly you need photos to show people - examples of your work. Then you need a portfolio book (old school) and a website with all your best work on to show potential punters. Then you need to get the people to see the photos. I would suggest spending a few Saturdays standing in your nearest towns handing out A5 flyers giving details of who you are, what you do, and how people find you/get in touch. If you had the portfolio sorted you could maybe carry it with you to show anyone who seems interested.
Will it be a work from home enterprise to start with, or do you have cash already for a dedicated studio?
Signs on your car is a good idea from Craig - if you get the magnetic ones, you can take them off when they would be a nuisance - don't forget other people can have them away quite easily too!
What about local radio? Contest where winner gets free photo package i.e. so many family portraits FOC?
Annual income twenty pounds, annual expenditure nineteen nineteen and six, result happiness. Annual income twenty pounds, annual expenditure twenty pounds ought and six, result misery