Assessing demand and making the call
Apartments move fast so you need to make decisions quickly. Did you hate the apartment? Move on, and see more. If you loved it, or liked it, you need to make a decision. First, get a sense for how likely it is that the apartment will stay on the market. Did it just get listed? Has it been available for days or weeks? Are there a lot of similar and available units in the same building? Once you gauge the demand for the apartment, make the call and act.
The reality is you'll never have 100 percent certainty in your decision, so you need to be comfortable with uncertainty. Are there better apartments out there? Will the next person put an application in? Assess demand, trust your instincts, make a decision, and be happy. No regrets!
Give clear feedback
If you're working with an agent, be upfront about what you liked and didn't like. If you don't give clear guidance, your agent can't find other apartments that match your feedback. If you've been clear about your needs, and you've seen ten or more apartments with the same agent, something's not working. Either that or your expectations are out of line. It will probably be time to find a new agent and adjust your expectations.
Once you've seen some apartments available, be ready to adjust your expectations, especially if you're new to NYC apartments.