This is a tactic that I think is so cool!!!
A friend of mine, who is very shy was trying to think of ways to spread the gospel and not draw attention to himself. SO he pulled out a phone book and picked random names and addresses.
He would send out a letter with no return address or with a corny return label like "heaven express" or something.
In the envelope he would place a tract, and depending on what the Lord lead him to do , sometimes he would put food gift cards, money or just a hand written letter.
Many people find this hard, because they want to see immediate results or be able to tick a box with how many people they "lead to the Lord". With this method, you never know what impact the planted seed will have, at least until we reach eternity!