Before discussing different strength and mobility exercises, we should first look at activation exercises for your Gluteus Maximus (referred to as the glutes) muscles. The reason for needing to activate your glutes is simple—as a population, we spend way too much time sitting, and as a result, what happens is what noted spinal researcher Stuart McGill terms gluteal amnesia—your glute muscles can "go to sleep" and not function properly.
When your glutes aren't functioning properly, other muscles (hamstrings and lumbar extensors) are called in to do the job of the glutes, mainly hip extension. Think of hip extension as the downward action of pedaling.
The problem is that these muscles aren't designed to be prime movers—they're designed to support the action of the glutes. Inability of activating the glutes can result in low back pain (low back muscles compensating), hamstring strains (overacting hamstrings), hip pain (resulting from hamstring-dominant hip extension) and knee pain (poor glute medius strength).
So, to activate your glutes, try the single-leg hip lift. Here's how it's done: