Pretty much the same - when I started, I also asked along the lines of "what did you do at the time of the incident?", often followed by answers like "I capsized" or "coughing out some water" or "getting back onto the boat".
Then I refined my tactics and asked whether there was any form of communication at the incident, often followed by puzzled faces and answers like "well, my tactitian called me a d*** for hitting the other boat".

After a while, I realized there really is no need to beat around the bush and I simply tend to ask "How did you inform Paul here you wanted to protest?"
Everybody in the room knows what to say when asked whether "the word" had been used and will answer accordingly - usually elaborating a long and sophisticated question only puzzles people and they have no clue what the heck that judge really wants.
In my experience, if a protestor missed to hail protest, they will admit it even when they are asked directly..

I usually say,  The racing rules of sailing require you as the protestor to do something after the incident, please tell me what you did. Please don't describe  the incident,  that will be discussed during the hearing.

The rules of evidence don't necessarily apply to an administrative hearing.  In the US, federal law states that the judge "may apply rules designed to assure production of the most credible evidence available, including allowing the cross-examination of witnesses."  And I think the value of the evidence depends on acquiring it in a manner not tainted by leading questions.  

While the judges manual discourages allowing leading questions WSJM - K17, it also leaves open the possibility for the chairman to allow them.  And I find that being obtuse regarding validity only adds to the awkwardness and stress the competitor feels at the start of a hearing.  If they don't understand that they needed to hail protest, asking them "what did you do to notify the other party you intended to protest" is not going to lead them to give false evidence.  But asking a general question usually leaves the competitor confused as Thorsten suggests.  And then they are guessing what it is you're asking and feeling stressed and confused, from which they don't recover very quickly.  But you do find out interesting information you don't otherwise learn, such as what the tactician thinks of the skipper...

The wording I usually used is; "at the time of the incident, how did you inform the other boat that you felt he may have broken a rule?"
Not saying the word protest in the question makes it less leading.

How about when the protest form clearly indicates that the protestor did what was needed?  Couldn't we safely be more direct then?  In those cases, isn't the hail and flag "asked and answered?"

Isn't the protest-form evidence from the protestor regarding validity and other aspects of the incident ... as we rely upon it for filing times, identifying the incident and the parties?

So we get a protest-form, and the Protestor clearly writes:

Is there a reason not to start there?  

To pick nits, the rules don't require the protestee to see the flag or hear the hail. But I do think this is a useful way to approach it - if the protestee agrees that the hail and flag were done then the PC can accept that they were, if the protestee doesn't agree then perhaps more questions are needed to establish to the PC's satisfaction whether notification was proper or not.

Overall I don't see any value in being coy about this question. "How did you inform the protestee of your intention to protest" seems appropriate and not overly leading to me. And I'll admit that if the answer wasn't specific enough I might lead a little further, perhaps "specifically what words did you use in your hail?", or (particularly if the competitor is inexperienced), "Rule 61.1 lists specific requirements for informing the protestee. Can you take a look at that rule and tell me how you met those requirements?". 

I don't think I'd feel right about dismissing a protest as invalid just because a competitor didn't independently and voluntarily tell me that they'd used the word "protest" (suppose that they did hail "protest" on the water but didn't realize it was critical to tell the PC they'd used that specific word?)

Bear in mind that while the official protest form asks these questions, the Rules do not require use of the official form, nor that the questions be answered.

Correct. The premise of the statement is that the information was " .. in the protest filing .. ", which must be in writing.

 RYA  Casebook 1999/1

QUESTION 3 Should a protest committee investigate the promptness of the hail and (when applicable) the flag in all cases, or only when the protestee makes an objection?

ANSWER 3 The purpose of the flag and hail is to do as much as is practical afloat to make the protestee aware of a potential protest. If the protest form claims that the flag and hail were prompt, and when the protestee does not, when asked, dispute this, the objective of the rule has been achieved, and there is no need to investigate further. When the protest form is ambiguous or silent, or when the protestee objects on this point, the protest committee must investigate.

I like the RYA approach above. 

So we get a protest-form, and the Protestor clearly writes:

If written on the form, I avoid all the confusing questions and go straight to the 'Any objections'.

"It says here on the form, that the protestor hailed 'Protest' within 5 seconds."
"Does anyone have any objections?  No.  Then let's consider this a valid protest, and continue."

Often the protestee will complain they didn't see or hear.  Sometimes genuine, but often a poor wild-stab-in-the-dark attempt to get out of the hearing.  Whatever!...the rules don't require them to have necessarily been heard or seen.  Go back to the protestor and investigate further.

If those lines on the form are ambiguous or silent, then simply be direct.  "Protestor, how did you inform the other boat of your intent to protest?" And go from there.

Benjamin, thanks for pointing-out that RYA Case as well as sharing your insights and process.  I think this dialog has been very helpful. - Ang

That's the easy version. The harder version is:

PC: "Does anyone have any objections?"

Protestee: "Yes. I saw the flag but it was at least 30 seconds after the incident, maybe longer."

Agree with Angelo!

Keep in mind that in courts, you are not allowed to ask leading questions to your own witnesses, but you can ask leading questions to opposition witnesses. Also, the proponent of a witness is usually allowed to ask leading questions if the thrust of the question is to provide background information.