XP is calculated like this
a chapter is worth 2-4 xp on average( a completed session but not a finished chapter is 1-2xp)
bonus xp is given for completing bonus objectives, using your head, ( ie say your mission si to infiltrate a building, a bonus xp might be possibel if you go to the library and get the blueprints for the building and use them to get inside, or if robbing a bank, kidnapping the bank manager at his house and having him open the safe before it open...doing research on a ghost to discover the local legend, who he was, how he died, where he is buried etc etc
playing your character well can give you much more xp, or hidden rewards...as GI Joe use to saw..."Knowing is half the battle!"
on top of that high end enemies, liek bosses imposible situations, solving huge mysteries etc, net bonus xp( normally this end of a prelude, or story xp tho ranging in 2-4 bonus xp..matching the challenge
any questions, feel free to ask, as always you can request new rules, rule changes etc in the thread