How do I pick up multiple units at the same time with the Medivac?

In some videos I've seen Medivacs scoop up a whole load of units at the same time. I'm trying to get by right-clicking all the units to pick them up, but knowing how to do this properly would of course be helpful.

Solution 1:

Instead of selecting the Medivacs and right-clicking the units, select the ground units and right-click the Medivac. They will all jump in immediately.

When Medivacs drop off units, they do it one-by-one, but they can load multiple units at once. This is very handy for rescuing units under fire.

Solution 2:

If you're used to queueing (and you should be!), then another method is to hold down shift and right-click units individually. The advantage of this is that you can then queue up a move order or even an unload order (although this will only be available once the medivac is holding a unit) after the load order(s), which can be useful to quickly relocate troops, but it's less useful with multiple medivacs.

This is true of overlords and warp prisms, too.