Walls and Ceilings - Removing leak stains on a ceiling...

What is the best way to do it?

You really can't remove the stains, you'll need to hide them with a stain blocker/sealer type primer. I generally use Kilz. Zinser also makes a good one. Both are available at the big box home stores.

And to add to what TG said..the latex based stain blockers aren't as good for water stains IIRC. Since the carrier/solvent in a latex is water...the stain bleeds though. Of course it somewhat depends on how bad the stain is...I have used latex Kilz on very light stains and it seemed to do ok.

You may need either an oil base or shellac based...and that can give a different sheen to the top coat of paint. Oh, and the shellac based wil have a lot of fumes. Good ventilation is a must with oil or shellac.

I wouldn't use a latex primer on any water stain. Often when they do cover the stain - the stain comes back later:wall:

Oil base primers [like original kilz] will cover most stains. Stubborn stains will require a pigmented shellac sealer like zinnser's BIN.

The primer shouldn't affect the sheen of the top coat [provided the entire wall was properly sealed at some point] It will take the top coat longer to dry and settle down to the correct sheen.

If the area is soft,crumbly,loose etc it needs repair.Do not prime or paint over an area that isn't 100% solid and intact.If possible examine the area on the other side and check for mold.