I have some names with no middle initials. Consequently, I end up with two spaces between the first name and the last name. Which of the "other placeholders" do I use to get rid of the extra space. If <MiddleInitial> is blank, then remove a space. I know it is not that simple but that is what I need the mail merge to do.

Perhaps you could explain what this has to do with *Ask, *Fill In, etc?

Assuming this is indeed for a mailmerge, you could use field coding like:
{MERGEFIELD First_Name}{IF{MERGEFIELD Middle_Name}<> "" " {MERGEFIELD Middle_Name}"} {MERGEFIELD Last_Name}
or:
«First_Name}{IF«Middle_Name»<> "" " «Middle_Name»"} «Last_Name»

Note: The field brace pairs (i.e. '{ }') for the above examples are all created in the document itself, via Ctrl-F9 (Cmd-F9 on a Mac); you can't simply type them or copy & paste them from this message. Nor is it practicable to add them via any of the standard Word dialogues. Likewise, you can't type or copy & paste the chevrons (i.e. '« »') - they're part of the actual mergefields, which you can insert from the mailmerge toolbar. The spaces represented in the field construction are all required.

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]