Business Cards are the cheapest form of advertising! Think about every way you can distribute them: put them in envelopes with your bill payments (you never know who is going to open the envelope and if they or their friends or families might need your services), put them in fish bowls at restaurants when you are trying to win a free lunch (I've gotten business that way…I didn't win the lunch but this was WAY better!) and see if local businesses have a place to display customers’ cards.
The one thing you want to make sure of is that you are using a professionally designed and printed card. Using an online printer who uses stock designs doesn't let your own individuality shine! In my possession right now are three identically-designed cards. They all have the same stock design and the only difference is their personal information. One card is for a picture frame company, one card is for a personal trainer and one card is for a painter. Brand recognition is so important and your card should reflect your 'brand' - whether that means a product, your personality or both!
When I design for my clients, I consider who they are and use that as a starting point. I like to meet for a bit so I can learn a little about them and take those feelings and translate them into print.
And, don't even get me started talking about paper stock! I could go on about the importance of tactile sense and aesthetic pleasure...but that's a Tidbit for another time!