Prod with aggression in early rounds until you find an exploitable pattern, or your opponent pushes back.
If you find an exploitable pattern, go about exploiting it. The most bread-and-butter early-round pattern is when someone calls frequently to see a lot of flops but only plays beyond the flop if he really has something. Another is someone who plays too tightly preflop and never 3-bets you with less than premiums. You can bully someone like this out of all his chips without ever seeing a showdown.
If your opponent pushes back in the early rounds, play a more small-ball approach in early rounds and watch for exploitable patterns in later rounds.
If you follow this algorithm to the late rounds, and your opponent still hasn't shown you a pattern to exploit, he is probably better than you, and heads-up is going to be more difficult than you can overcome with some strategy pointers.
Also, watch for tells. You're going to get to see the same guy do the same thing over and over, and it will give you more opportunities to catch things that may give you an edge from hand to hand.
Caveat: You may not want to beat your friend this mercilessly if you want him to keep playing with you.