Funny you should I ask - I just came across this great post about protein-moisture balancing.
You can do a 'strand test/ wet assesment' as described in the article, and you can find out if your hair needs moisture, protein or is balanced.
If you do a strand test (pull a strand of hair, and see how it behaves) and you get any of the results below, you need more protein:
(When Wet or Dry) Stretches a little more than normal then breaks, you need more protein in your regimen.
(When Wet or Dry)Stretches, stretches, stretches with no significant breakage yet, add a bit more protein to your regimen.
(Wet)- Feels weak, gummy, mushy, or limp, you need to add more protein to your regimen.
The Fine Art of Protein and Moisture Balancing for Black Hair Care - Yahoo! Voices - voices.yahoo.com