The best way is to actually look like a clan that people want to join.

If you go around making big things about trying to destroy other clans because they supposedly made someone else leave JJ2, people will think your clan is really immature and they won't want to join.

You should also try and drift away from the hotel\employee room idea, because those are not popular anymore.

And most of all, you need to make sure that you are a good player of JJ2, and then other good players and bad players alike will want to join the clan.

Other things: A good website helps too