Two keys to the transition. One, you want everyone topped off going into the second phase cause the first stomp will hurt a lot. This means even though you are burning the feet to push the phase as soon as possible, you can't let yourself get tunnel vision and take extra damage from something like a magma flow. Two, you need to kinda learn the sweet spot for ranged to group up behind the boss such that AoE healing can hit the melee as well, but the ranged are not being knocked back. It's helpful if melee stands close to their max range so that it is easier for the ranged to gauge where to stand. One of the few things that can cause the second phase to go sour is healers not healing to their full potential or ranged dps not burning to their full potential because they took a knockback that could have been avoided. Some groups may also choose to pop a cooldown for the first stomp to help while the raid repositions however if the raid was topped off before the phase started it shouldn't be necessary.