Hmm, very interesting question. Back when I started with SL, I had no idea what to do. I usually asked to other avatars, but most of them were as newbie as I was or were too busy on their own bussiness, so they paid me little to none attention. Since my main goal on SL was (and still is) to become a builder, I gradually met friends on classes and sandboxes. In a nutshell, at the begining, my SL had little social contact.
After a long pause of my SL due to RL schedule conflicts, I came back but, to my surprise, most of my old contact of my list never came back to SL. On the other hand, I realized I became more social on this SL "rebirth", meeting anumber of new friends. Long story short: When my friends don't appear, I just park my avie in a sandbox and build, like the old times!