With the Look At That! game, Leslie McDevitt suggests you start teaching it in a low distraction area using a neutral object - you can hold something behind your back, whip it out and cue your dog to look at it, and when she does, mark and reward. It helps if your dog already responds to a clicker or verbal marker and will immediately turn back to you for a reward when they hear the marker. You want her to "get" the game before trying it out in the real world around any triggers.
Part of the reasoning behind it is that not allowing dogs to check out things that they are anxious about can actually be more stressful, so rather than using "watch" or "leave it" to keep your dog's focus on you instead of the trigger (which is not always easy if she's worried about something over there), you give her permission to check it out. Also, as Cschmidt pointed out, there's a counter-conditioning element to it, the sight of a trigger becomes a cue to interact with you in a familiar game, which can help diffuse stress - it puts what Leslie calls a "rule structure" to the situation.
An important part of LAT is that the dog gets to look at the trigger, but is not under any pressure to interact with it. Once you've started the LAT game, your dog shouldn't meet the other dog, it's a look but don't touch protocol. If she's relaxed and wants to meet the other dog and you know the dog is also friendly and you'd like them to meet, you would clearly release her from the game first. Some people like to have a "go say hi" cue to use after the release, to signal to her that it's okay to meet the dog, although if she doesn't want to it's better to avoid greetings at all.
One thing I like about it too, is that with the game you can get a lot of brief glances rather than prolonged staring. Both of my dogs will sometimes bark at other dogs when they're on leash, and eye contact is a huge trigger, so anything that will break up that eye contact and redirect them to me for a treat will diffuse that. I cue them to look, I mark it, they turn back to me and get a treat. Rinse, repeat a few times, and by then the other dog has passed us by.
If you haven't read Control Unleashed I would highly recommend it. Leslie has a yahoo email list and she participates daily, answering questions and helping people, along with her moderators. But in order to not be on a "read only" basis on the list and to be able to post, you have to have read the book first so everyone is familiar with the general concepts and the specific exercises, to avoid having to explain it over and over again.
This link talks about the training progression of LAT!: Raising K9: Leslie McDevitt's LOOK AT THAT! Game