Tips for efficient AS3
AS3, like many OOP languages, contains many micro/macro-optimization techniques, that may be unheard of to inexperience users. To help the less experienced ones : What are the tips worth knowing, that will enrich an AS3 programmer.

Since most as3 programmer, will use either flash or flex, programming tips involving them are naturally welcomed too.

Also please limit each answer to one tip, so the best ones will naturally float to the top =)
Tips for efficient AS3
===

AS3, like many OOP languages, contains many micro/macro-optimization techniques, that may be unheard of to inexperience users. To help the less experienced ones : What are the tips worth knowing, that will enrich an AS3 programmer.

Since most as3 programmer, will use either flash or flex, programming tips involving them are naturally welcomed too.

Also please limit each answer to one tip, so the best ones will naturally float to the top =)