Bluff more when you are heads up because you only have to get through one player. It’s way easier than trying to bluff more players. More players means more of a chance someone has something to call you with.
If you are heads up and your opponent has capped his range, these are the spots to look for.
Most importantly, make sure before you even think of
bluffing that you are not doing this to a calling station. Can he even fold?
Make sure your bets are meaningful. Putting someone’s tournament life at risk close to the money when you know this player really wants to cash could be another good spot.
Lots of good spots, pay attention and you can find them.