Credibility is key
Look professional. Get your business cards; have a business name; have a letterhead; get a website; show that you've got some substance about you.
In terms of making the overtures to try to win business, have an attitude of understanding what the potential client might want instead of pushing yourself as a person that they should engage.
Take two different coloured highlighter pens when you go to see a lawyer about a lease and ask them to highlight all of your rights and obligations in one colour and all the landlord's in another. You come away with a colour-coded document, which a lot of small businesses find to be a practical thing, because they can look at it and they've had it explained to them.
Source: Mark Brennan