I agree with Judi as well. I stay in touch with my past clients regularly all year. Throughout the year I direct mail/email my own 2-page bi-monthly Newsletter. It is true that some past clients prefer phone calls, emails while others like getting my Newsletters via US Mail. I stay with a farming area (years) that makes sense to my business plan. The majority of my business is referrals.
There is no quick and easy route to obtaining quality clients. I find the best advertising is getting out of the office and meet folks face-to-face. Most commercialized mailings (post cards) will be round-filed, and these mailings tell a potential client very little about you, who you are, and what you have to offer them above the norm.
In my opinion, sending out personalized and well written materials will capture attention because the perception is you are talking to folks, not at folks. Good luck to you and I wish you all the best in your endeavors.