a dumb thing to do is start making a solo out of nothing..cause then you have to make a riff FOR the solo and that sucks. and the solo wont be that good cause you have nothing to like.. feed it of
as for leads you do the same thing. play a riff in the background and improvise a lead over it until you're happy
check out my licks on the metal section. maybe you'll find some of it useful
Bøniz
Mrdriller!