learning from tabs book

i,am working on lead guitar, when trying to learn a song from guitar world magazines,do i learn just the lead parts,or would i learn start to finnish,need some input,thanks,

Learn as much as you can? That's usually the best way to do anything.

Always. Even if you're playing the lead guitar in any song, it's still good to know the rhythm too. So yeah, learn every possible bit you can.