I can never remember the order of the shorthand property for setting the margin or padding in one declaration. That is:
margin-top: 2px;
margin-bottom: 4px;
m
Whenever you strike with a given situation, just think of a clock-wise rotation i.e., way the clock rotates from 0 to 60 in a circular rotation.
Clock thing is easier to remember than the word TRouBLe (as marked answer) in my opinion since the word trouble
belongs to English language and all those minds native to English language might find it easier to remember the word TRouBLe in relevancy to the given situation but not others who only use English language when they really have to.
Same is not true with clock-wise rotation of a clock, when it comes to remembering something (as asked it the question) since clock-wise-rotation is a very well-known phenomena world-wise.