So I've heard mention of HIIT, but I haven't found anything on the site explaining how it works, and how to go about doing it? Since it's the most efficient fat burner, I would like to incorporate this into my workout but I don't know what exactly you are supposed to do.

I only use ellipticals because of my knees, and I feel like I get a good work out, but I would like to try this.

HIIT is where you would add higher intensity levels then back down to a lower level. I have not done it on the elliptical but I am sure it would work.
What I have done is walk for say 3.5 mph then run 5.5 for a minute (or two) then back down. I know some its really high for shorter periods of time.
On the elliptical I would guess you would do it either with HARD resistance trying to keep the same pace.. or else focus on accelerating the pace up for a minute... such as if you do about 140 do 180 for 30 seconds or a minute.. .
then back for a few minutes..then just do sets of these....
Good Luck

If you google, you will see a variety of websites touching on it.

I think Body for Life has a pretty good HIIT plan.

http://www.bodyforlife.com/exercise/cardiotraining.asp

Basically, you change your intensity throughout your workout going from moderate to very intense in regular intervals.

I've done it two ways....

1. Every 30 seconds, I bump the intensity or the speed up on whatever cardio machine I'm on. I go up and down every 30 seconds, using the slow 30 seconds as my recovery time. Sometimes I do this method in 60 second increments.

2. The second way I do it is to listen to a podcast from Stin (free on itunes) where she takes you through a 20 minute HIIT routine. Two minutes of warm up, then she takes you up a 'level' each minute. You decide what your levels are but it's the same premise of increasing speed or resistance. So, two minutes warm up, 1 minute each at level 6, 7, 8 & 9 then repeat a total of 4 times ending with 1 minute at level 10 and a cool down.

At this point, I can't say it has positively impacted my weight REMOVAL but I can certainly notice it in my fitness level. The long slow burn way of doing cardio is fine - but I get so incredibly bored. With the HIIT sessions, even if I do 2 of them, they are more interesting and I'm amazed at how much more I can do, intensitywise.

A lot of ellipticals have them programmed in. The one I use it at level 8 for the low and I think 16 for the hight, it really just depends on the machine. If you're just starting the interval you might want to start be only going up a level or two for the high period just to make sure you don't over exert. I do it this way every day, they are 60sec intervals if I do a 30 min workout and 120sec intervals if I do a 60min workout on that machine.