How do you know if someone is making a play on you?

[ismisus]

Background: a 20+2 PokerStars tourney. Early stages, blinds are only 15/30, I've been just moved to a new table. They think I am very aggressive, since the first two hands on the table I won big pots with AK and KK without showing.

CO:1635
Dealer(hero): 2925
SB: 1370
BB: 4870

Hand: Folds around to CO(1635) who raises the min to 60. In the dealer I have KQ, and I choose not to re-raise in position. Since I raised the last two pots, people won't respect my raise. So I just called 60. Good idea? SB folds. BB(4870) calls.

Flop: Qs 3s 5h Pot:195
BB checks
CO bets 120
Hero: I call, I got top pair. I am only scared of the Ace coming out, just want to seeing how many chips will CO donate to me.
BB: Calls 120, I did not expect this, but he has a big stack, might be loose

Turn: Qs 3s 5h 4c. Pot 595
BB checks
CO bets just 90
Hero: raise to 300, don't want anyone to draw too cheap
BB: ALL IN FOR 4690
CO: folds
Hero: I think he's bluffing, this play just makes no sense to me. Why is he going all in, after playng this hand so weak. Did he draw for an inside straight? Well don't worry, I folded. However is this the right fold?

Additional hand with BB.
Blinds 25/50
All in Raiser(5980), now in UTG raises to 150
Hero in the BB(2640), just Calls with JJ /images/graemlins/smile.gif
Flop: 4 5 5
He bets 100, I raise to 300, he re-raises to 1200, I re-raise him all in, he folds.

Now was he bluffing the first hand or not?

[Colombo]

Just because he folded in example 2 doesnt mean he was bluffing. A good player could fold AA there.

[Harv72b]

I also think he's bluffing in the first hand, although it's very possible that he's holding an overpair/set & panicked at the 3-straight showing. Some people just like to push with a strong hand & hope someone calls with a weaker one.

Tough call & a tough fold, too. If you're best you more than double up into a great chip position, but if you're not you're out. I think I'd take the chance in the early stages of a MTT.

***disclaimer: I'm far from an expert on the matter***