LFG also provides a really efficient way to screen people. Sometimes you can tell somebody's competence just by their response. One player might say, "Yoooo hit me up for the raid." while another might say "Hey, I'm playing X character and I'm at X level. Mind if I join?" Simple things like that allows you to determine how much of a team player and communicater one might be. You can also easily search their username whilst you're on the computer to see their gear.