The aggression issues that I work with really vary, Anywhere from resource guarding and cage-aggression to fear biting and, occasionally, the big strong dog that's always been allowed to run the household. Cage aggression is actually the most common problem I work with - the dogs are very good once they get out, but getting them to calm down long enough to touch the cage and let them out is challenging. I do use treats with cage guarders, but my absence is the biggest reward for them. Most of the dogs put on a big show, snarling, growling, throwing themselves against the gate etc when I start walking towards their cage. I will stand right in front of the cage while they throw a fit, without making eye contact or doing anything threatening. The instant they stop, even if it's to take a breath, I click, throw some meat to them (doggie treats just don't cut it when they're so agitated) and immediately back off a few steps. If they stay quiet, I leave entirely. Over a period of a week or so, I build up the period of time the dog has to stay quiet in order to get me to back off. Once they will settle down with the word "shush", I stop making my absense their reward and start letting them out to play instead. Once they realize that a person approaching their cage means that they get to go out, it's no longer an issue.
Honestly I pretty much use that technique with all "outside-the-cage" aggression too, whether they be fearful, overly assertive or just plain don't like strangers. If they don't want me around, I walk away. That's their reward for calm behavior - the thing making them uncomfortable (me) leaves. Once they are safe enough to be around, I spend "quality time" with them and build up some trust, then start working on that same calm behavior around other people. As soon as the dog stops displaying aggression, the behavior is marked, the dog gets a really good treat and the person walks away. Once the person is able to get close enough to the dog, they drop a treat on the ground right before they walk away. Most of the dogs I've worked with never really like strange people, but they at least tolerate their presence. I also help with the placement of the dogs I've worked with, since I know them well and know what kind of home they'll need. I was working on typing up a little booklet of information for the people who adopt the formerly aggressive dogs from the shelter, just so they know how to prevent problems, but I never got around to finishing it.
I'm really not sure if that's a "good" way to go or not, which is why I'm so eager to meet good trainers and pick their brains, as well as take some courses on behavior. What I've been doing has been working well, but there may be a better way out there that I don't know about. Part of the fun of training, for me, is learning and trying new or different techniques.