(Postcard, yellow letter, etc.)- What message is conveyed in your mailings?

So I got my post cards printed up to send out to some houses I am interested on trying to get under contract. 

I carefully crafted my first postcard.

when it's cold, like now, deals are plentiful, but take longer to flip.bandit signs, direct mail postcards, online classifieds, newspaper classifieds, bird dogs, flyers, business card referrals (offer cash), neighborhood farming, etc, etc will all bring you leads.

I am attempting to compile a tax delinquent list to market postcards to, for the city of Newark (first timer) and I have a question.

I don't strategically place them, I use postcards and yellow letters strategically. 

I've been wholesaling for a while now grinding out postcards and internet leads with private sellers, but the MLS was an enigma.

Anyone have or can point me to some examples of letters, postcards, etc. that have worked?

(letter or postcard?)

I'd like to use every method known to man, but realistically 100% direct mail letters/postcards will probably be my initial method.