Nordie,
I am going to take a two cent stab at this...
First of all, don't let Bam Bam tighten it for you

, whatever the part is that is leaking will need to be replaced because he'll break it off completely.

Hi Brad!

Are we talking AN fittings? Something that is more common than you realize is that AN has a different face angle than a standard flare fitting, so if you are trying to get an AN to seal on a flare, chances are you will have some issues..
I am making assumptions here, but AN is pretty straight forward.
Is this on water or fuel/oil? if water, try some PTFE paste on the line first, then just a dab on the flare...Got a picture of it?
GT