What should you look for when you go into the even viewer in Windows?
Is there any events that are more important that others?
Of course but its not just easy to know what you should be looking for, going to this site and you will have a better overview of what EventID there is.
A little list over important security related events
EventID - Event
4782 - The password hash an account was accessed
4720 - A user account was created
4722 - A user account was enabled
4740 - A user account was locked out
4625 - An account failed to log on
4649 - A replay attack was detected
4728 - A member was added to a security-enabled global group