One of the key components of the specific job I do for my employer, a pest control company, is grow the business in my region. I spend a lot of time meeting with people in person doing this, and generally I have a lot of success this way (last I knew, all of the new monthly accounts our company gained last month were all generated by me). There's one major problem inherent to this sales approach, however: my finite being - I can only be in one place at one time!
For what I'm doing, and for business people in general, mass marketing is the way to go. The "conversion ratio" may be small (i.e. the number of individuals sent advertisements versus the number that respond), but the expense is worth it since you can essentially be more places at once. And getting a sale right away isn't necessarily important since your advertising efforts can at least notify people of the existence of your business, which later on can turn into a sale.
Custom Postcards are one way to go about doing this mass marketing stuff, and it is something that I might try. A colorful postcard briefly detailing the services one's business offers can find their way into a potential customer's notebook, stuck to the front of their refridgerator, etc. Then, when the need arises, your name and number are right there and probably easily remembered by the client.
Of course, this costs money, but you can save a little by using this coupon code at Vistaprint: PC50. This code is good for 50 free oversized postcards. Could you use fifty more customers? How about fifty more customers for the price of postage? I know I could, and the return on the investment would be astronomical!