Lists: Avoiding ArgumentOutOfRangeException: Argument is out of range errors

Hi, I'm trying to expand my knowledge of Lists and I've been experimenting the last few days. My current focus is on avoiding ArgumentOutOfRangeException: Argument is out of range errors when other functions or scripts are accessing a List that is constantly being updated. Even checking if an element in a List is actually there before doing something can still result in these errors, so I am guessing between checking and doing, the List has changed. My next focus of attention is here: http://msdn.microsoft.com/en-us/library/3azh197k%28v=vs.110%29.aspx Am I on the right track or does anyone have some solid advice on how best to avoid out of index scenarios? Thanks!