Don't waste energy pulling back. Just pull STRAIGHT up. Also, make sure you are standing directly over the centerstand. The stand on our scooters sits farther back than the stands on regular motorcycles, so I know I tend to stand towards the middle of the bike (where the stand is on my K1200LT) and not by the passenger saddle (where the stand ACTUALLY is). That makes it a LOT harder.
Also, because the stand is so far back, I can imagine some people MIGHT have an issue holding on to the left handlebar and standing in the proper position without turning the bar to the left. It might be best to NOT hold the handlebar. Once you have both "feet" of the stand on the ground, you really don't need to steady it with the handlebar anyway.
Finally, make sure the sidestand is UP when you attempt to put the bike on the centerstand. If the sidestand is down, it locks the rear wheel so it won't roll. If the rear wheel doesn't roll, it'll make it that much harder to lever the bike up onto the centerstand as you'll have to DRAG the back of the bike the first couple of inches before the wheel leaves the ground.
That is all.