In citations, how to find out if it's a compound name?
The convention, inasmuch as one exists, is:
Write the name the way the individual wants it to be written.
For example, one of my co-authors has four names:
(First Name) (Middle Name) (Adopted Married Name) (Given Last Name)
but chooses to use
(First Initial). (Middle Name) (Adopted Initial). (Last Name)
as his "formal" academic name.
As a more concrete example of this phenomenon, this is a significant issue with a lot of British folks, who eschew the hyphen in a "double-barreled" last name. For instance, you'd cite:
Vaughan Williams, Ralph. The Lark Ascending. London: Oxford University Press (2005).
and not
Williams, Ralph V. The Lark Ascending. London: Oxford University Press (2005).
In such cases, you just need to look up exactly how the author writes his or her name, and follow that trend. Google Scholar can be a good source of such information; Web of Science and other citation-tracking sites are often better.
The most useful method of all would be to find "self-citations": works where the author cites his or her own work. How the name is written under those circumstances should be the most unambiguous statement.
You could google the person and see how they refer to themself in their publications on their group's page. This would probably be the easiest general way to solve this problem.
No.
(aeismail has already addressed nicely how to deal with this, but what follows is too long for a comment.)
As far as I know, there's no standard way (i.e., the same for every name no matter the culture) of indicating which components of a name are considered to be the last name. In fact, even the concept of last name is different from culture to culture and may even be absent -- see http://en.wikipedia.org/wiki/Category:Names_by_culture. Even in Europe, you can get quite complicated naming systems. So you are really trying to identify the "main professional name", whatever that may map to in a given culture. To identify it from the list of names as written within that culture, you have be familiar with the specific naming conventions (maybe the Wikipedia page helps, or if you know someone from that culture, you can ask them).
It's worth keeping in mind that getting it right serves two purposes:
Making sure everybody knows the person you refer to, even if they don't know the full name.
Showing courtesy towards that person.
While the second point is the only one of importance when addressing the person directly ("Dear Professor/Dr. X"), in your case the first point is actually more important: If (say) a referee wants to check the bibliography whether you cited a relevant author's works, they would expect to find them in a certain form. If everybody uses the same (wrong) way of parsing the name, it would arguably be the right thing to do to follow that choice.
(Finally, you could also chicken out and just list all authors in full, native name order; in Bibtex, you can do this by wrapping the full name in curly braces.)