Here are the steps I'd recommend:

1. Pick out a dozen startups whose products/services REALLY interest you.

2. Formulate a couple of interesting thoughts/questions/ideas about each of them. This link provides some general ones to ask. You should also think about a few very specific to the startup's product/service.
http://blogs.hbr.org/cs/2012/08/...

3. Try to reach out to people who work at the startup through a variety of ways. For e.g. through shared contacts, an alma mater in common, writing brief inmails on Linkedin, or sharing your ideas with @theirtwitterhandle and getting to know their community manager, etc.

4. Learn from these discussions.

5. Repeat with more startups.