1. Well Defined Support/Resistance Level
The first pre-requisite to identifying a healthy pre-breakout situation is having a clearly defined barrier in the form of a support or resistance level. The classic case is when you have a trend in place (lets say uptrend) and then the price action runs into resistance at a key level.
Ideally, you want there to be at least two touches on this level before defining it. The more horizontal and neater this level is - the better. But it should be noted, this is just a pre-requisite and generally by itself not enough to identify a healthy breakout setup. The reason for the two touches is to identify a sticking point where players are parked and what level they are defending that the (bulls in this case) are unable to penetrate.