Well, nothing work more wonderous than having a good word of mouth marketing when dealing with small businesses. Try to gain as much reputation as you can by being of actual service to your customers and then be proactive to get a reference from them.

Go to business networking luncheons and if by god's grace you ever get a chance to speak publicly to small business community then grab that with both your hands as it will give you unthinkable publicity. Advertise on local news papers and look at other other low-cost methods of advertising.

Try to gain a portfolio of customers in simmilar bussinesses and with that portfolio in hand, go and approach the rest. It will make you look more credible.

Good Luck!