Depends on what your timeline is.
What you tend to find is that when you arrive at a listing you are typically the 8th person there and two people have already handed in deposit checks (as in sorry, you're too late). You have maybe 10-20 minutes to act on a fresh craigslist ad to reserve as early as possible a time to check the place out (arrive at least 30 minutes early because other people do) and bring all the necessary documentation with you already. My advice is to find yourself housing early because it is a giant pain in the @#$ trying to find anything decent on manhattan. It's a seller's market, and demand is much greater than supply, thus forcing you to be much more proactive should you hope to be successful.