In game would be fastest, probably. Then Guild then forum post. You could make a post in the recruitment section and give your levels. If you're social and nice in general, I'd try Asterisk for a guild.
And leeching is only leeching when one person is doing the killing and another is generally just sitting back getting the experience. When two people are working together and supporting each other but still sharing exp. it's just leveling together, I think.
