how to fix a damp stain?

How do I treat a water stain from an old leak on the ceiling, I have tried a blocking spray and three coats of emulsion, any old tricks of the trade would be appreciated.
Jim, January 2010


done
make sure ceiling is absolutely dry rub area down then put primer on patch

yeswot, February 2010
hi jim been a decorator 4 20 yrs best way too cover is use gloss paint on stain may need 2 coats but always works for me once you are sure its stopped the stain just emulsion over

shaun webb, January 2010