lasso tool

Hi I'm new to icon-making, and this is probably going to be a stupid question. Okay, I've checked the memory for this community, and I've noticed several mentions on the lasso tool. Then I went to play with it on my psp8. I made it to work, but I've also selected other junk in the process. In the to

from mini-movie tutorial by crumblingwalls, the selection is pretty clean. What's the best way to achieve this? Thanks to any advices.