If the plant is mature enough, you'll see a flower stalk growing. That's the beginning of the plant knowing that it is getting to be spring time. Otherwise, later, you will begin to see the new leaves are more upright, and the traps will be the largest of the season. That is when you will know that the hibernation time has ended.

Based on various discussions last spring, this dormancy break time could happen as early as March and as late as May for people growing in different regions of USA. If you're somewhere else, just keep this kind of time frame in mind that it's not the same for every area.