When you go to promote your site. Don't be shy, be very outgoing, calm, and informative about your site.

Try to say as much as you can in your ad about your site. Don't be like, "Please join my site. It is very cool."
Now I could explain a book about my site rather than 8 words. So next time you go to advertise your site, stay cool, and be informative.

Not to Disagree with what you said I TOTALLY agree!!! But , Do not yell it doesn't make people want to join.

DO NOTs:
[hr]
1 - YELL
2 - SWEAR
3 - CRITICIZE
4 - FORCE

DOs: (what Dan_Clk said)
[hr]
1 - BE AFFIRMATIVE
2 - BE OUT GOING
3 - STAY COOL
4 - STAY VERY CALM

Yes as Dan_clk said, when promoting you need to big up your forum as much as possible and not be shy

And as 1ruleyou said don't yell or criticize...when promoting expect some criticism and most of it is constructive..use the feeback instead of getting angry someone had a fault with your forum