A few things to keep in mind ..........
1) Dog should already be neutered.
2) Dog should be current on vaccines.
3) Dog should either be on heartworm prevention or test negative within the past 30 days.
4) I would also recommend having the owner (if your going the route of newspaper, etc), sign over the dog to you. Nothing fancy, just something on a piece of paper that states they gave (or sold)the dog to you. Be sure it has their name(s), address, & phone number on it and they actually sign & date the note. If you end up adopting from a rescue group or purchase from a responsible breeder, they will have you sign a contract.