Get a Database of your Farm Area, do the reverse directory and find the correct info of your farm.  Correct name , address etc Send direct mail rather than indirect mail, send cards for all ocassions if possible, they will not forget you, especially occassions like birthday  always hand written, start with a small farm about 100 names and keep adding to it....the secret is the personal touches you make, because you have taken the time to get all this info together....

More ideas on getting names, try the phone cd directory or white pages.