you deffinately have to know your tunes, also when it comes to mixing structure it, don't pick your favourite dubstep tunes and mix them together in most cases it won't work, choose songs that will perfectly compliment each other. Either with melody or bass

I Completely disagree, theres nothing better than a double drop (if you get it right), mixing intros is ok but it's a starter, as you get better at mixing expand make the mixes longer make the basslines compliment each other blowing audience away with huge mass of Bass! Got a couple of double drops ...