Mechanics review
 

Just to refine and clarify mechanics as written, not to debate the merits of any instruction or one book versus the other.
Main interest NFHS/ASA, but add NCAA if you like.

Are these really taboos?
- calling OBS at a base by the PU
- calling OBS at HP by the BU

- BU calling infield fly
- BU signaling but not calling infield fly

- PU making a call at 3rd from slightly in foul ground
- Same, runner returning after rounding

Multiple runners, lead runner to 3rd, no play at home:
- second play; PU or not
- first play after possible play at 1st not made; PU or not

Are you just asking us to vote our opinions?

ASA:
Are these really taboos?
- calling OBS at a base by the PU - NO
- calling OBS at HP by the BU - YES

- BU calling infield fly - YES
- BU signaling but not calling infield fly - NO

- PU making a call at 3rd from slightly in foul ground - Depends on the call in question and the situation
- Same, runner returning after rounding - ditto

Multiple runners, lead runner to 3rd, no play at home:
- second play; PU or not - I pregame this, every game.
- first play after possible play at 1st not made; PU or not - First play is BU's (assuming 1st play not at plate)

Although what I expected, I am surprised at everyone's complete agreement.
Please expand on those above.

How do you handle this?
B slot, runner goes to 2nd on passed ball. Do you continue to C immediately or stay at 2nd and actually wait for ball back to pitcher?

The first play, I'm not sure what situation you are referring to - PU could be at 3rd for a number of reasons, and could be right on the play, or 50 feet away - so my answer depends on what kind of play you're referring to.

The second one, I ALWAYS include in the pregame that I, as PU, will cover the 2nd play at 3rd if BU is taken to 1st for the 1st play. As BU, I describe the scenario to partner and get his input (sometimes they do it, sometimes they don't like it and expect BU to take both calls). It may not be ASA standard, but it's at least 50/50 here, so I want to make sure I'm on the same page as partner.

I know it's not standard, but I'm seeing it more lately --- I rim the infield on this play, getting to the SS side of the bag ahead of the runner (but not all the way to C yet), watching ball, pitcher primarily and watching for the touch of 2nd and/or obstruction by glancing over.

On a PB where there will be no play on the runner coming in to 2B I do this as well. If she continues on to 3B I am ready to follow, and if there is a throw to 2B to try to pick her off rounding too far I am in the correct spot for the possible tag call as she dives back into 2B.

Stay with the runner by rounding the base. If there is going to be a play there, this will give you the perfect view of the front edge of the base.

Inside?
 

Does anyone cut inside behind the runner as she approaches 2nd?

Not on that play.

And step in front of a possible throw?

If she continues on to third, isn't that PU's coverage?

OP stipulated no possible throw.

And the umpire would know that how? Just because there is no immediate play does not mean the catcher will not try to throw behind the runner rounding or that the pitcher will not try to pick-off the runner if she is off the base when the ball is received in the circle.

I'll come inside....kind of. I like to come in after the runner passes, then close down to second base on a direct line from 1st. That gives a great angle for a possible pick off on an over run (90º to the tag). Watch the ball go back to P then move to the C position.

Hugo's question:

"If she continues on to third, isn't that PU's coverage?"

Maybe........Situation is single runner on first advancing to second on a PB, then to third. Have got to pre game this every time and watch for your partner. Typically, I take all single runners to third, even on PB situations. Plate umpire may be blocked, especially if the PB goes to the 3rd base side. Plate may be unable to go to third without risking getting into the play. Better to plan on covering from the base side as you don't have anything else going on.