For HOW, I have already decided treasure of any type is its own reward. I believe the actions and successes a character makes should provide a tangible reward as well as being a reflection of their abilities.
With all of that in mind, I'd like to propose the following simple system for HOW:
For any test roll (attack, defense, spell cast, skill use, etc.) a character makes that succeeds, the numerical difference between your target number and your dice roll is awarded as XP.
Example: Toshiro Redcap attempts to pick the pocket of wealthy merchant. He needs a 10 or less to succeed. Toshiro rolls a 7 succeeding. 10(goal)-7(roll)= 3 XP rewarded.
For each additional die used in a roll for a test (instead of 3 dice you rolled 4 dice or 5 dice) you get +4 XP points added to the success difference.
That's it, clean and simple. Now no matter what type of adventure (combat heavy, trading, thieving, etc.) you run, any time a test is successfully made, the character is rewarded. Also if your are more successful in a test attempt, you automatically get more points! If you are more skilled, you will start generating more points to reflect that as well. Indeed there will be additional referee optional rewards for game play...but the core XP generating model is that simple formula.
I will have to re-figure the math, but initially, I still believe 100xp x New bonus level works as a method for increasing the ability, or learning, new skills. (+1 bonus=100xp, +2 bonus-200xp, etc.)
Yes I am still NOT letting attributes be increased with XP, only skills. This gets rid of the Conan the Librarian issues, and places finite limits, of a sort, on each character. Blame it on my like of characters like Batman, Green Arrow, Captain America and the Falcon if you like. I prefer the skilled ultimate human hero, over the super human hero. This should allow unique heroes that need each other to succeed over the high fantasy indestructible type.
Comments or concerns are welcome.