You'll definitely be able to tell if you go overboard with protein. Unfortunately a lot of this is trial and error. I'm able to do a strong PT once a week and rotate in a protein heavy RO once or twice each week in addition. I basically figured it out by increasing the strength and duration of my PTs and not seeing any signs of too much protein. Then I started adding the protein RO several weeks ago.

3a/f/iii
Modified CG since 11/5/11
CLEANSE: VO5 Vanilla Mint Tea Clarifying, DevaCare No-Poo, CHS Treatment Shampoo
RO: DevaCare One Condition, SS Caitlin's Conditioner, Mop Top Daily Conditioner
LI: SS Repairing Protein Treatment, CHS Silk Leave-In
STYLE: Re:Coil, Curl Keeper, Deva Ultra Defining Gel, Curls Rock Amplifier and Strong Hold Mousse, Sweet Curls Elixirs Okra Gel and Hard Hold Gel, SS Curl Enhancing Jelly and Firm Hold Gel