As I said I want experience to be based on the actions of the character, not the player.
First and foremost, I'll keep the "completion award" for completing "adventures" or scenarios, a reward for success seems to be good. I might adjust it a bit down.
Further a flat one point reward per session. WW has done this for some time, and I think it's a good idea. a plain reward for taking part in the game.
Apart from that I want my players to gain XP from using their skills, So my idea is this: every time the player rolls a knack (or attribute), he puts a mark next to the knack used, only one mark per knack, when you have ten marks you erase all the marks and get an XP. at the end of the scenario, you erase all the marks and note down how many you had, these count as free marks at the beginning of the next scenario.
Of course if a player RPs a knack use without rolling (unlikely in my gaming group, we like dice) the GM can assign him a mark for the relevant knack.
Likewise if a player starts "tick-hunting" the GM can refuse him ticks for irrelevant rolls.