As doc_study said, the bacteria (or fungus) would be eating the glucose for energy, and the virus wouldn't, so the glucose would be low in bacterial or fungal meningitis but normal in viral meningitis - this is one of the key diagnostic features of the CSF tap.
Protein could be normal or elevated in viral meningitis. As doc_study said, inflammation will raise levels. Protein will especially be raised in bacterial or fungal meningitis - I think of it as the presence of antibodies, though I'm not sure if that's accurate.
hope that helped a little...