I started off making my avatar look as close as possible to how I did in RL at the time. Middle-aged man, 6 feet tall, quite slim, with a mop of greying hair. I also wore similar clothes - jeans and t shirts. Since then the two appearances have diverged. In RL I now have a beard and my hair is a bit shorter and a bit greyer. In Second Life I now have a shaved head (something I've never had in RL) and I have put on a lot of weight (which I've also managed to avoid doing so far in RL). I'm about 5 stone heavier in SL than RL - it's probably unusual that way round! But I'm now a much snappier dresser in SL, with my generous girth concealed by an ankle length gold satin great-coat and a stylish black top hat!