Twist jumps can seem harder than they really are during your first attempts because many lean into the twist at take-off – this causes you to travel (nearly always) slightly forwards and to the side at the same time as you are twisting with an inevitable loss of balance.
The correct technique requires you to start the jump as much like a straight jump as possible and, as you near the point of last contact you twist your arms and shoulders upwards into the direction of twist – this is like coiling a spring. As you leave the trampoline the friction previously keeping your feet in place no longer exists – this allows the spring to uncoil and your feet now join in the twist; continuing to ‘reach round’ the twist with your arms and shoulders helps complete further twist which should now be lean-free.
For more, faster, twist we can also do this with arms stretched out to the side at take-off and then, like an ice-skater or ballet-dancer, bring them into line – this will cause a large acceleration of twist because of the rules of Conservation of Momentum. At no point in this exercise should your head or shoulders be anywhere other than directly above your feet.