Regardless of bike I always start with a skidplate, handgaurds, and if watercooled, radiator protection. From there, you need to decide how hard you intend to beat on it.
On my 690 I have:
case covers: http://www.adventure-spec.com/defaul...m-690-e-r.html
brake pedal/shifter tethers: http://www.rockymountainatvmc.com/p/...er/brake+snake
brake pedal: http://www.cleanspeedeng.com/Brake%20Pedal.htm
tubular radiator cage: bought from Nomadic cycle racks years ago, but they no longer have it on their website... they would probably still make one if you asked nicely.
techspec to cover vulnerable areas on the sides of the tank: http://techspec-usa.com/product_info...cts_id=351&i=s
Chain guide gaurd: http://shop.bulletproofdesigns.com/p...&categoryId=30
I haven't purchased it yet, but I have managed to bend 2 rear rotors now so a rear brake rotor "shark fin" is definately on my list: http://www.scottsperformance.com/Pro...2&Bike_ID=4657
I ride in extremely rocky places and ride the 690 like a real dirtbike and these parts have all helped to make sure that I can ride back to camp. Just 2 weeks ago I had a bad get-off (lucky to be alive) on the 690 at 55-60mph in the desert while riding through rock strewn whoops... bike faired well other than breaking the bar mounts and some damage to the top triple clamp.
If you ride stuff like this, I think what I have is "reasonable protection" but is most likely overkill for casual forest road riding: