In no specific order;
>Never spam, that'll instantly put you in the category of a noob random recruiting clan.
>Use GWG, I've gotten a few people by just making a good post in the guild database. Make it good though, as there's A LOT of total BS there.
>Pick and choose, go for quality over quantity.
>Test them - actually play with potential recruits as SOT wisely suggested.
>The language - full sentences, respectful, intelligent. Use this form while talknig to potential recruits.
>Ambition, you need to have it otherwise your guild will fail. If you can't handle the heat, get out of the kitchen.
>Persistence, without it you will again fail. In the world of MMO's a 25% recovery rate of already recruited people that are truely good is normal. This means that 1 of 4 (recruit) out of the 20 people that you attemped to recruit.
>Luck - it's always good to have

>Personality type, in relation to you. If you're not social then there's a problem with you being in the recruitment position.
>Your guild scope, give them something to join - not just "another clan." This one is hard if you don't have the right combo. Think about it, then adapt to the correct answer.
That's all I can think of for now,
Good luck to you and your guild!
-Ascension