There is one strategy that is used in sit and go tournaments, often enough that, once observed, it can be exploited.
The strategy is simple enough. Early on in the tournament, simply wait for good cards and fold on all misses. The main goal here is loosing as little as possible, minimizing risk, and only going to showdown with premium hands. Depending on how the cards run and whether other players learn to back off if they are calling strong, players can double up or more over time.
I have even seen players completely sit out the first two blind levels so that there stats (for those following stats with the HUD) will appear very tight.
In the first case, the goal here is to portray the rock playing style. The hand history on these players only shows strong hands, so no clues as to the upcoming gear change from history. And, any heads up display hand tracking software will give them very tight statistics, leading players to believe that pre-flop raises indicate strong holdings, the same for post flop action.
The players who completely sit out the first two blind levels are doing the extreme version of this. The software will still track the hands played even as they sit out, leading to the conclusion that, based on soley on stats, they are playing tight.
The second tournament strategy is easier to pick out, as usually players who sit out for the first two blind levels then enter the game loose and aggressive. Wait for strong holdings and let them bet into you. When they suddenly start playing hands, establish range as quickly as possible. Also, a player sitting out for the first few rounds might as well have a flashing light above their name, as soon as they sit back in their playing style is put under the microscope for possible exploitation.
The first fake rock strategy however can be tougher to spot, the first clue is usually the person is suddenly increasing the number of hands they participate in.
The second clue is based on a change in playing style. Rocks only raise when they have strong holdings, but suddenly this player is raising one off the button to steal blinds and doing large continuation bets after every pre-flop raise. The key here is to notice the FREQUENCY of these moves. Rocks make them very occasionally, fake rocks make them more often than they don't.
This second clue is key, as a real rock sometimes gets on a rush of good hands, its important to attempt to find the difference between a rush and a change in gears.
Another clue is folding to a re-raise after a continuation bet. This is a situation that a rock is unlikely to find themselves in, they would only bet if they have hit strong, and would usually have a hand that can defend against a re-raise. Observe this in another players hand and know that you are most likely no longer dealing with a rock.
A combination of these clues and others can identify the fake rock rather quickly as the action heats up with the final table. Keep your range calculations on this player dynamic, and rely more on recent hand history than stats over entire tournament playing style.
An especially devastating move these fake rocks like to employ is the deadly all in. If you have played an entire tournament with a player who appears tight, and then moves all in when you have top pair good kicker, this puts you in a tough spot.
The only thing to do here is to have established recent range. And keep very close track of exactly how the hand played out. A fake rock is going to be check raising and highly aggressive and loose in most hands. A real rock will not. Stick to your hands when you have decent holdings against them, lower what you will call them with.
If you can put these clues together, sudden increase in number of hands played, recent hand history indicating lowering range, and especially an increase in aggressiveness on all streets, then the fake rock trick may be under play.
As you can see from this post and the min raise post, there are situations where, even with the same player, you might fold to a min raise, but call an all in. A fake rock suddenly going aggressive will only min raise on the nuts, but will push all in to get you off a hand.
Putting this all together can lead to the hero call on a post flop all in bluff.