Another key thing and is probably obvious but something our coach used to go on about is three key areas physicality, endurance and knowledge.
You have to be able to win beat your opposite man around the park, in the contact area and outthink him. The guy we used to always look at was George Smith, he used to be (and still is) dynamite at the breakdown, smash people in tackles but also chose what was worth competing for and what was not. I'd 100% have a look at his play and how he managed his game.
Other good small backrowers I'd suggest are Neil Back, Michael Jones (NZ & Samoa - great ball skills), Francois Pienaar (fantastic guy and player), Fergus Slattery, Thierry Dusautoir and maybe an old stalewart of prem rugby such as a Julian Salvi