I used to set up a word document and put maybe 6 boxes on an A4 then write rhetoric or copy bits from women's magazines (I say I, I really mean the wife did it) but they just took up too much time they did do quite well but you do have to look at hassle v outcome, postcards are far easier you have no hassles remembering to get them out the return is not quite the same and customers don't keep them as long but realistically you want an instant response.
Shaun