Try and remember what you eat in the cafeteria (or take notes and write it down). There are many books for dieters (and web sites too) that help you calculate what the nutritonal value of different foods are. You can also look up a lot of them here:
http://www.nal.usda.gov/fnic/foodcomp/search/
You don't need to know EXACTLY, but a good idea of the nutrients of what you're eating is definatley a start.
If I have to eat at a buffet/cafeteria type setting, I try to look for the following:
-dishes with whole recognizeable vegetables
-dishes with large pieces of meat. Preferably fish or chicken.
-a minimal amount of thick sauces, etc.
-try to avoid obviously greasy or fatty foods
I drink a lot of milk. Some guys have problems digesting it, but not I. I love it. I say keep it in your diet, as it has good protein. As well, milk can help moderate insulin spikes if you drink it with a sugary meal. That's good. If you want to cut down on the fat, then skim milk isn't a bad idea, but personally I'd leave it in. I'd rather drink milk (whole if need be) and find other places to cut out the fat. Note that SOME fat is good to eat. You don't want to eliminate it completely. (of course, if you're lactose intolerant then you might want to rethink that)