getting your calls/letters to stand out: tips and tricks

To the experts on the board. what are some tips & tricks you use to get your calls and voicemails to stand out over others? what are some tips and tricks you use to get a better response from you letters and postcards. I live in phoenix and am currentyly mailint postcards to pre' foreclosures. I mail 2 postcards in week 1 and 2 and then send 2 more 5 weeks prior to sale. I have been sending out mailers( first letters and then postcards) for what seems like forever. Everyonce in a while i get a voice mail. I call back immediately but they never answer and never return my call. I want to improve my presentation over what they are receiving from everyone else. Please advise. cjs cjs111@cox.net