This just happens to be another of those frequently asked questions -- about when or IF a player should hold his or her hockey stick in one or two hands. So, always aiming to please, here's my recommendation...
-- Dennis Chighisola
Two Hands or One on the Hockey Stick
The short answer to part of that question is that, a player absolutely has to control his or her stick in two hands at certain times, and then in one hand at certain other times! Given that, I always separate the rest of this question into two parts -- as in when a player is on offense, and when he or she is on defense. Stick Grips While On Defense
When our opponents control the puck and we're away from the opposition puckhandler, there are generally two things we can do...

At yet other times we may be positioned to intercept a pass between the opposition puckhandler and his or her open teammate.
In both instances, it's obviously necessary for the defender to have both hands on the hockey stick.
When our opponents control the puck and we're responsible for dealing with the puckcarrier, I feel it can be hugely beneficial to use one hand on the stick for a period of time...
Whether we're in a body-checking or non-checking game, it's necessary for a defensive player to veer the puckcarrier in a given direction (usually towards the outside, towards the boards, or generally towards an area where he or she is easier to trap). This steering is best down while approaching from an angle and also holding the stick in one hand -- using it sort of like a steering tool. Nowadays, however, with the new checking rules, I recommend that the defender switch to two hands as he or she closes-in on the puckcarrier.
By the way... The use of one hand on the stick is also necessary as a backward skating defenseman plays an attacker in a 1 on 1 situation.
Stick Grips While On Offense
Any time an offensive player wants to be available for a pass, it's obviously important for him or her to give a stick-target and to ultimately try to receive a pass while holding the stick in two hands.

In yet another 1 against 1 situation, it is often easier for a player to protect the puck by holding it far out and away from a nearby defender (as in the above photo).
So, as I hope you'll appreciate, there are different times during the game action when it's advantageous for a hockey player to hold his or her stick in either one hand or two.