It all depends on your area, the type of tenants and how they want to communicate. My tenants for example are usually younger and computer savvy and thus use the internet, e-mail and text messaging to communicate. We have a website (through our property management software company) that generates most of our leads. The management software also automatically posts ads on craigslist and other sites, which also generates numerous leads. We hardly use yard signs anymore and the daily paper is no good and too expensive.
In other areas, I have friends who have to use yard signs because their prospective tenants are not connected or do not read the paper or are driving around a particular neighborhood they wish to live in. I have one investor friend who even hires people to hand out fliers at supermarkets advertising his rentals.
So it just depends on how your prospective tenants want to communicate. You have to figure that out. Good luck!