hotmail account was hacked

My hotmail was hacked last night. Someone sent out spam emails to people to my contact lists. I know that it is easy to send out emails pretending to be me simply by inputting my email address in the "from" field, but this person actually had access to my contact list....

SO far that I know, this can only be done if they have my password.

As a precautionary method, I have changed my password. However, I am concerned about preventing this from happening in the future.

My password was pretty strong to begin with, it has more than 6 digits. I also have taken care not to use hotmail on public computers. Only in my home and office computer, (and recently my cell phone).

To access websites that I even remotely consider as doubtful (I havent dealt with before, etc), I use a virtual computer using virtual box. I don't use the virtual computer to access my hotmail.

So my question are:
1. To prevent this from happening again in the future, what can I possibly do to ensure this won't happen again?

2. How (really, what does it take) did they do it?
I did not access my hotmail from any other link than www.hotmail.com
The only thing I noticed was that I cannot access hotmail a few days ago, and the error l;ink page is a bit unusual. But I checked the login page I inputted and it was correct.

3. How do I know if hotmail password is the only thing they retrieved? And not other passwords like the one I'm using to access Expert Exchange or other services?