I won't pay them, never did. The best way is to get a recommendation from another writer already signed by, or who simply knows, that agent. It's a screening process of sorts. You can subscribe to Written By , the WGA's monthly journal, even if you're not an agent. The Mystery Writers of America is strong, and I believe you can join as an associate member even if you're not qualified to join as a pro.
Many top organizations are like that.
You meet people more successful than yourself and they like your work and refer you. Tennessee because he was so gracious and so damn funny, invited me into his home. Spielberg because he's so in love with what he does and so upfront about it. Spielberg was expecting the cover and should have had it, since he's a huge Boy Scout supporter and created the cinematography badge. Tell us about your new online course you are teaching.