OTB score keeping

In descriptive, though, each move is named from the point of view of the side making it, but both players keep annotating the same, of course.

No. That's what make algebraic the, in my view, superior system - a2 is a2 regardless of your perspective.
(Although if white is moving his pawn to a2 then you've set the board up incorrectly.)

Side note: Descriptive notation, which Pulpoferia mentioned above, hasn't really been used in decades. So I wouldn't worry too much about it. Algebraic notation has been the standard since the early 1980's.

If you are very new; you can check your notation by looking at your opponent's. They should be the same. (I don't think any opponent will object if you just look at his/her score sheet. If he/she does object, then just ask to see it at the end of the game and take a picture to verify yours.)

If I'm not mistaken, at tournaments and such players are generally required to sign each other's score sheets as well as their own.

There's part 2 as well...

depends on what annotation you're using. If you're using the e4, Nf3, style then the square f4 is the same for both sides. however if you're using the P-K4, N-KB3, style of annotation then it's all about perspective. Your score sheet should still be the same as your opponents. as when you write down their move you write it down from their perspective.