mechanic question: dead ball vs. down indication

[chymechowder]

This isn't a big deal, just something I've wondered about for a while and can't seem to get an answer.

I'm a linesman/line judge in Mass. high school. My question is:

Is there a standard for WHEN you're supposed to indicate the down? Specifically, when do you change from a dead ball signal to a down-indicating signal?

Say it's first and ten. A22 carries for 7 yards to my side of the field; he's tackled halfway between the hash and the sideline. I get the end of the run, square up on the sideline, come in a few steps and hold my spot.

At this point I've got my hand up for a dead ball. After the umpire spots the ball, I'll change to a 2nd down signal above my head and walk backwards to the sideline.

Now, I know alot of guys will just come in from the get go with the 2nd down signal. (they don't do the dead ball signal).

Is one way preferable over the other?

(It can be different depending on the play, I realize. Like if there's a fumble but Team A recovers, you might signal (and announce) 2nd down the whole time to indicate who recovered. Or if you KNOW he's a yard short of the line to gain, you might only do the 2nd down to tell the ref he's short and we don't need to take a look with regard to the sticks.)

But I'm talking about "garden variety" plays. Not a big deal, I know. Just wondering. Thanks.