How a goalie should prepare before games can be approached differently by each inividual and depenant to the kind of schedule you may have to endure.
Preparation for a goalie is huge and if possible, should start a few days before game night. From experience when I played at Carleton University, I knew that game day was every weekend; starting in Fridays game meant I started focusing on the game early in the week. I would know what opposing players to look for on the ice. Who had the most goals, points, etc. In a CIS short season, I knew every game counted and I had to be at my best everytime. I started to prepare myself by working hard in practice and getting a good feel for the puck all week. I would specificaly work on tracking pucks ensured I played out all my rebounds to recreate a ame urgency.
It was a very different story when I played Major Junior. While playing in the QMJHL, there are a lot more games and lot less time to prepare. To focus on the long schedule there is very little room for error. We as goalies are in our own world and we have to figure out our own time to get ready and focus on each game. Regardless of the schedule, preparing always included a lot of small focuses. Maintaining your body is lways important even if its as simple as drinking water, being rested and eating properly. I would often warm up with a ball pre game and focus on tracking the ball into my gloves. I would have a talk with my goalie coach before and between periods.
When it comes down to the game, no matter the level, all these little mental and physical ways to prepare helped me raise the level of your my game. As a coach I now encourage all goalies to come up with a routine that is unique to them and consistent every week/day. Preperation has always been a big component of any success I've enjoyed.