How do you check if a square is a magic square?

Could you please explain to me, in a step-by-step manner, how one might go about verifying if a given square arrangement of numbers is indeed a magic square? I'm particularly interested in understanding the criteria and methods used to confirm its magical properties, such as the sum of all numbers in each row, column, and diagonal being equal. Additionally, are there any specific rules or patterns that I should be aware of when performing this check?