Craigslist is number one for rental stuff (in my book). We also use lots of other sites through our internet listing syndication process.
Agent networking is also a big key because a LOT of stuff gets rented by agent to agent networking.
Sign calls are also important - perhaps more important on rentals than on properties listed for sale.
Also, make sure you have a realtor lockbox for showings if possible.
Rentals are doing pretty well in the area right now.
We do lots of rental listings in Dacula/Buford area if you want an local broker.