When to apply the modifier to make it real??

Well i made this character and now i wana rigg it… i used a mirror modifer to make it and also subsurf … now at what point shall i click on the apply button to make the modfiers real… before wiegth painting or when??? and is it important?

you have to apply the mirror before you begin assigning weights,
otherwise youll get weird results. the subsurf you dont apply ever. (That means it shouldn`t ever be necessary to do so, there may be cases but you can worry about them later)


Of course, it never hurts to either copy the object first, or save the blend file as a different name so you can always go back and tweak the modifiers if you discovered something you missed.