Search engine submissions

At what point, or does it matter, should I submit my site to the major search engines?

I just got it up and running, but still make minor changes daily, but are mostly visual changes.   I have added the meta tags to the pages, and I think I have covered all my basis...

My forum is for people trying to lose weight, I was approached by some friends off another forum where there were too many 'rules'.  But in order for us to stay active, we need to be found.  I don't want to jump the gun and submit to early if I am not ready.. but if it doens't matter, then I will do it now.

Thanks for your constant help here!