Take the word(s) in a clue and try to use it in a sentence or two,
and see if that leads you to a suitable answer. For example, [Clouds
(up)] could be included in “The sky clouds up” (darkens) or “The
window clouds up” (fogs). See if one of the alternatives that come to
mind might have the needed number of letters.
Ask a friend for a hint or an answer. Let’s say sports isn’t your
strong point—ask a sports fan, “Who’s a 3-letter Boston Bruins
great?” and she may offer up ORR.
Pull out a dictionary, atlas or other reference book, or use a search
engine. The dictionary compilation site onelook.com allows you to
enter an incomplete letter pattern to generate a list of
possibilities. For example, keying in BL??D? yields a list of words
including Blanda, bleeds, blends, blinds, blonde, blonds, bloods and
bloody. See if one of those matches up with your clue.
Visit the New York Times Today’s Puzzle forum
(http://forums.nytimes.com/top/opinion/readersopinions/forums/crosswordsgames/todayspuzzle/index.html)
or a crossword blog such as Diary of a Crossword Fiend
(http://crosswordfiend.blogspot.com) to find hints or ask specific
questions about the puzzle.
Another time-tested approach is to put the puzzle aside and come back
to it a little while later, or the next day. Many solvers find an
intractable puzzle becomes much more manageable with a fresh
perspective.
The last recourse is to check the answer grid the next day (or in the
back of the crossword book). Reread the clues and make sure you
understand the connection between the clue and answer.