How do you choose beginnings?

To be honest I've been working on my current novel for quite a while now and am facing a challenge - I have no idea how to start my novel. I mean I started it several times, but then came to the point when there was nowhere for novel to go. These beginnings were definitely wrong.
Are there any ways to tell whether the beginning you are working with is the one you need?

Literary Agents

I've been recently researching Internet for agents who accept romance submissions. Here are some quite useful links:

http://joanswan.com/romance.agents.htm
http://www.michelesinclair.com/agents.shtml

These are lists with agents' names which I found to be very useful.