Hello guys!
Credit to: Wolverabid, PurplePoot, Silvenon, Paskovich

I want to make a list of things that leak and things that optimizes.

Dynamic Unitgroups
This trigger will instantly destroy dynamically generated unitgroups.
Trigger
Events
Event

Conditions
Conditions

Actions
Custom script: set bj_wantDestroyGroup = true
Unit Group - Pick every unit in (Playable Map Area) and do (Unit - Hide (Picked unit))






Another way to avoid a group leak is to store the group instantly to a variable, and then destroy it manually.
Set GroupVar = Pick every unit in (Playable Map Area)
Unit Group - Pick every unit in GroupVar and do (Unit - Hide (Picked unit))
Custom script: call DestroyGroup(udg_GroupVar)


This is useful is you want to use the group more than one time in the trigger.

Dynamic Locations
Unit - Create 1 unit at Somewhere



If Somewhere is a function, like (Position of (Unit)) or (Center of (Region)), it will leak.

Set loc = Somewhere
Unit - Create 1 unit at loc
Custom script: call RemoveLocation(udg_loc)




Player Group
Note: (All Players) does not leak, and destroying it can result in problems
Player Groups leak also, but those are really rare. The fix:
Player Group
Events
Unit - A unit Starts the effect of an ability

Conditions
(Ability being cast) Equal to Some Spell

Actions
Set PlayerGroup = (All enemies of Player 1 (Red))
Player Group - Pick every player in PlayerGroup and do (Do nothing)
Custom script: call DestroyForce(udg_PlayerGroup)






Sounds
Also sounds leak, they should be destroyed like this:
Sound
Events
Unit - A unit Starts the effect of an ability

Conditions
(Ability being cast) Equal to Some Spell

Actions
Sound - Play (Some Sound)
Sound - Destroy (Last played sound)






Special Effects
Speical Effect
Events
Unit - A unit Starts the effect of an ability

Conditions
(Ability being cast) Equal to Some Spell

Actions
Set Point = (Position of (Triggering unit))
Special Effect - Create a special effect at Point using Abilities\Spells\Human\ThunderClap\ThunderClapCaster.mdl
Special Effect - Destroy (Last created special effect)





Please add your experiences