This is simple to do but hard to master basically you run then point at the ground and fire at the same time as jumping and you shall jump a lot high than you normally do.BUT BE CAREFUL YOU NEED TO HAVE ARMOUR TO USE THIS BECAUSE ITS NOT EXACTLY GOOD FOR YOUR HEALTH.
This is very hard to learn and twice as hard to
master. To do this you fire a grenade and make it land out in an
open area
just before it explodes you run and do a rocket
jump (see above for rocket jump) so when you do your rocket jump it is
at the exact same time as the grenade explodes.