It's all about speed thru the ball, and (of course) hitting the ball first, and compressing it against the turf. You'll want to use your sand wedge here.

Set up with the ball back in your stance (open to the target) and focus on the -front- of the ball.  Take the club back a few feet and accelerate -thru- the hitting zone, cutting your follow-thru short.  That's where you get the "zip".  Remember, ball-first, then turf.  You'll want to 'clip' the ball.

What MMHarmon32 said... but also remember not to lift up the clubhead. 

I struggle with this shot too. I have a hard time keeping it low. Mine usually just balloon up because I didn't maintain the shaft angle through impact.

To combat this, focus on having more weight on your front foot (lean toward the hole).  A forward-press move as a swing trigger might help, too.  To start your backswing, lean the butt end of the grip a half inch toward the hole to kind of 'trigger' your shot.  Then, just keep your wrists from hinging during your shot.

We asked Jordan Spieth about this shot and here is what he had to say...

Great video Mike! Thanks for sourcing it and posting for us. It's great to see Jordan explain his thought process ... especially after we have been watching him pull off shots like this throughout the year!

Jan,

      The commitment to this shot is just the same as a flop shot (ever tried hitting a flop shot while not being 100% certain you'll pull it off?) Only disaster can occur if you don't stay with the shot. Harmon above me hit it spot on. The only thing I would emphasize is placing a little more weight on your front foot, something like a 70/30. Also, try not to confuse spin with ball flight. Your first impulse would be to think that if you want spin, you need the most lofted club...this isn't true with this particular shot. If you want the low spinner, grab a 52 or 56 and play that club. You'll get marginally less spin than with a 58/60 but you will get the ball flight you desire.

If you can afford it, I also recommend getting different bounces for different wedges. You could basically give yourself one wedge for low spinners and one for high floaters. Why use multiple swings with one wedge when you can use the same swing and just change clubs for each different shot?

This was posted on GolfWRX yesterday. It might be helpful for you.

http://www.golfwrx.com/324662/the-science-of-adding-spin-to-your-wedge-shots/

Jan,

I like to practice these shots by chipping believe it or not. I like to hit low bump and run chips with a lot of check at the beginning and then the low trajectory and momentum allows the ball to roll out. You hit this with a shaft that's very forward, weight on left side, and hit down on the ball with a steep angle of decent. Compress the ball as much as you can and accelerate. Swinging through the ball with speed is key for this shot. If you can get the chip right then the low trajectory high spin shot is just a longer swing version of it, be warned full shots of this is not advised with a wedge since it is a high percentage shot and with the amount of spin on the ball it will balloon.