Personally - I do similar to what Chupup Games is saying, but I follow strict guidelines everytime:
Main ES (used for specific events that will be included in EVERY level)
Combat & Movement ES (used specifically for player combat and movement)
Global Variables ES (used for ONLY global variables; makes finding things easy)
Cheats ES (everyone's got to have cheats while testing
, but honestly this makes it easier to release your game without thinking "did I disable all the testing shortcuts I made...?")
Functions ES (ONLY contains functions)
Menu ES (all menu functions)
Then for each stage type I'll have an ES, so if you have 10 layouts of "Ice Stage", I would have ONE Ice Stage ES and put everything in there. It's the cleanest way to find things without having a single event sheet.
Hope that helps!