The wiki contains lots of pages where people have discussed aspects of running or creating a LARP.
Here is an index for them:
Running a LARP:
RefTeamComposition
ChessyPig/MakingLinearsBetter
ChessyPig/LinearStyles
Valtiel/CompetitiveLinears
Creating a LARP:
GeneralLARPPrinciples (somewhat outdated wrt TT)
SettingWriting
NPCLevels
TheInquisitor/LarpMagic
ChessyPig/ClassBalance
Chevron/SmallLARPeconomy