...you weigh 'em :-) when you get a new one, it's a good idea to mark it with the empty weightI'd love to switch to cornies, but how do you know how much is left in them?
I had trouble getting the lids to seal properly until some kind soul here explained that you need to initially take the pressure right up to seat the lid properly down onto the seal. You can sometimes hear them 'pop' a bit when you do this.
Also note that sometimes the lids seal better one way round than the other... I draw a line across the gap so I can get the alignment right.
My procedure is something like this:
1) remove & sterilise O ring, then rub with a little petroleum jelly (the seal... not you) and refit
2) fit lid in correct orientation and lock with lever
3) connect regulator then hold pressure vent open and flood headspace with CO2
4) let go the pressure vent then take the pressure right up until the lid pops (30psi should do it)
Incidentally, it's worth fitting a check (non-return) valve to your gas in disconnect if you want to avoid the risk of beer or foam somehow getting back up the line into your regulator.