Question: Is there a rule(s) of thumb that every chess player should know about the double pawns?
Since it hasn't been mentioned yet, I will also put that double pawns loses control of the squares infront of them.
Bad: They can't defend each other like adjacent pawns can.
Good: They give you an extra open file for your rooks.
Usually the bad outweighs the good, but there are a zillion exceptions. Most beginners are overly afraid of having doubled pawns.
Isolated double pawns are considered as weakness in general except rare occasions where they play a crucial role in defending important squares. There is no general rule of pawn islands with double pawns close to the centre and each case should be analyzed separately. These pawns are not considered as a weakness since they can either establish a strong centre or can be un-doubled easily.