Evaluating an opponent in a game you're familiar with?
Reading people like this is something that takes years of practice and experience.  there are no easy answers.  However, to get you started, here's something:

One common personality trait that distinguishes people, fairly 50/50, is risk-aversion.  

In such a game as you describe, ask yourself which of two strategies is more based on chance.

More risk averse people will choose a strategy that minimizes chance (variance), even at the expense of overall win percentage.  For example, in a dice game, a certain strategy might win only 40% of the time, but the decision of win/lose is more based on a player's positioning than the rolls of the dice.  Likewise, the 60% winning strategy can lose spectacularly, if lady luck isn't on the gambler's side.

In such a situation, a risk-averse personality will choose the 40% strategy more often because in the case of a win or lose, they can 'blame' themselves instead of luck, and a win feels more sweet, and a loss doesn't feel uncontrolled.

Determining risk-aversion is fairly simple before the game starts.  Everything from dress to occupation to speech patterns can betray one's temperament.  Salesmen tend to be gamblers, accountants risk-averse.  Suits: risk-averse. Flashy or colorful clothes: gamblers.  Tentative soft speakers: risk averse.  Loud, fast, highly social speakers, gamblers.

Enjoy!