And don't forget to crosscheck your documentation too. For example if you use the IAN approaches on a 737 you are not allowed to apply temp correction in the FMC for the approach waypoints, however you have to fill in the descent forecast page which does include an ISA correction and actual QNH, both are used to fly the correct glidepath on non precision approaches. Makes it easy as you do not have to fiddle around with the temp correction table much as the FMC takes care of that on its own.