1. Go into your Google Plus account "+ You" on any Google Page
Select Video Hangout
2. Go to your GMail page
Find a contact on the bottom-left corner
Hover over that contact
Click the camera button to start Hangout
3. Go to your Calendar page
Create a new event
Include video call
Invite other users
The event will contain a link to join video Call.
Here is a video demonstrating all of these methods.