A few things from when I used to recruit that I think worked and which I look for when joining somewhere new.
Be clear on your alliance requirements. Titan levels, special requirements for troops, tanks, TP
How casual or competitive.
Be a recognised face on the forum, generally if just seeing the person post in recruitment less likely to join, whereas if more active feels like more interested in the game and helping/ giving advice.
Have personality. Reading the same thing posted all the time is boring.