Scoring etiquette

For many reasons, you should always mark before you take the darts out of the board. I've even seen people pull their darts then forget what they scored. lol.

I think it's more or less a universal rule to either mark your round before pulling, or that the scorer, if present, should have entered the score before the darts are pulled. It saves a lot of confusion and sometimes suspicion to do it that way. 

It's also a good habit to develop because it's more likely to get you to the board quickly to touch at least one of your darts, officially ending your turn. If you've got a dart that's barely in the board, precariously close to falling out, as long as you physically touch any of the darts in the board, then they'll all count, whereas if one of them falls out as you're approaching, or fiddling around with the math, the errant dart will not have counted, whether you've called the score out or not. 

Leaving them in also affords your opponent(s) the opportunity to come up and check the hit if they can't really tell or question it. 

(True story: There's one particularly troublesome player in my local scene who is known to cheat regularly. He's an absolute clown that nobody takes seriously and most of us can't figure out why he's still allowed in our local dart bars since his antics routinely cause arguments and fights, but be that as it may: one of his usual tactics is to throw his darts, not call a score out audibly, pull them and then enter something higher than what was actually hit. He'll do it on checkouts, too, not just mid-leg turns. Once he pulls them, it creates a situation where it's one person's word against another with no evidence either way. That's a problem - and if it's a cash game, it's a good way to get lumped up outside for being a cheater. Ninety-five percent of the problem with this dingbat would be eliminated if he'd just call and mark his rounds before yanking the darts off the board.)

A low stress way to avoid issues if you're playing someone new is to just establish this before you begin your leg/set/match. It might feel awkward the first few times, but it helps avoid contentious situations like I've just described.

Call em, touch em, score em, pull em.