This is a Pine Tree. See how the needles are LONG?
Well, when you LONG for something, you PINE for it. So that is a good trick to remember the pine tree.
And this is a FIR tree! See how the needles are FLAT? FLAT and FIR both start with 'F'. And that is how you remember the fir tree!
And this is a Spruce tree! At first it is hard to tell it apart from the Fir tree.