Special requirements should be mentioned in the title, body and tags. Now, people could argue of the use of XeTeX is special or not. For me personally it is, because I'm a
pdflatex-only user. I remember a question about TTL fonts which only used the
xetex tag to indicate its usage. If the title would have contained any XeTeX reference I wouldn't even had a look on it, knowing this is not my area of expertise. However, I overlooked the tag and commented that TTL fonts are usable...
I wouldn't say it is needed. Question can be phrased in other ways. Having a lot of question starting with the same words doesn't make the site more readable.
Definitely. Like any headline or start of a sentence they should start with a capital letter, except if they start with a package or class name which IMHO should be written all lowercase like it is used in the code.
In general the title should be short and meaningful, but not to short of course. People should know from it what the question is about and if it seems likely that this question can be answered or is otherwise interesting for them. The titles are used on several places and should describe the question well. Titles like "Can you help me fixing this problem" doesn't say anything.