Thanks all, are there specific specs to look for in glue sticks other than diameter and "low" or "high" temp?
Adhesion to specific materials. What the stick is made of. Melting temperature. Working temperature. Etc etc etc.
For general purpose and non-critical use... just go buy some inexpensive all-temp sticks and see if they work. If not, try the hi temperature sticks. Generally the stuff in the craft stores (or craft section at your favorite big box store) will stick to a wide range of stuff - they're designed for crafts so sticking to any random thing you throw at them is a good property to have if you're selling them to crafters who *will* try to adhere almost any two items together with it.
For a commercial application you need to pay attention to the specifics like flexbility, working temperature (after it's been applied), adhesion (especially at temperature extremes), etc. etc. etc.
If you want a primer, go to one of the online stores which specialize in this stuff. For example, I find hotmelt.com to be a wealth of information. You could also go to a glue stick manufacturer's website... I find adhesivetech.com to be a good example.
Adhesives are always a pain to specify unless you're doing something very simple which has well-defined solutions (i.e. hot gluing boxes closed for shipping). As soon as you move out of that, the correct answer depends on so many factors that it's really best to experiment unless you're using them for something either professional and/or critical. At which point, it's best to find an adhesive expert who is going to ask you a lot of questions that you probably won't have answers to (I.E. is that a high or low energy plastic you're attempting to adhere to).
-forrest