When you’re playing in position you can be more selective about when you semi-bluff. Generally, semi-bluff raising a donk bet (when an opponent leads into you) will be the best line until you build up enough history to know what your opponent’s range is for doing this.
Let’s say you are 100 big blinds deep and open with Ks-Ts from the cutoff. You’re called by the big blind who also has 100BB. The flop is Qs-8c-5s. What should you do? It depends on your opponent and whether they are a nit, a very tough TAG, a crazy maniac LAG or a terrible weak-passive fish. Well, against all of them betting will be fine, but some of the time you should check too.
Against the nit you should check back a lot of the time as they will give away their hand strength on the turn. If they check-raise the flop it’s terrible for you because you’re rarely going to get the money into the middle in great shape and calling to try to hit the turn is a huge leak.
Versus the tough TAG you can balance betting and checking back in the same way as against the nit, but for different reasons. Generally it will be far harder to force these guys to make big mistakes so checking back adds a layer of deception to your range and can induce a bluff on the turn.
Against the maniac LAG you can definitely bet out and look to jam all-in over their check-raise because you dominate so much of their range, which includes many hands they’ll have to pass.
Against the weak-passive fish, betting to build the pot is a nice line, knowing that if you connect with a King or a spade you can extract more bets from them.
A final word of warning
Be careful about semi-bluffing boards against very aggressive or crazy players where you have showdown strength and/or nut draw potential, such as A-J on a Q-T-4 rainbow flop or J-T offsuit on an 8c-9s-Ks board. In the first example you probably only get called by a better hand which means you have to fire multiple streets with your gutshot and overcard. In the second you may get check-raised by a wide range of hands which will prevent you from seeing some turns and rivers.