There are 3 different ways to have start Google Hangout.
1: From Gmail.
When you are logged in to your Gmail, you can see on the left hand side there is a toolbar that says Hangouts. If it isn’t there, click the blue Sign In button. You enter the information of who you’d like to hang out with into the white box that says “New Hangout.” If your friend is in your Google contacts, just type their name. You can also type a gmail address or a phone number. (The first time you will need to enter their information to find them, but after that their name will appear in a list. Most recent Hangouts are nearer the top.) As you start to type a name or email, different options of contacts will appear underneath. When you click on the correct one, a Chat Box will open. Type and send like any other chat. Congratulations! You’re hanging out! To add others to the conversation or advance to a video chat, click the option at the top of the text box. To video chat you must have a web cam and Broadband connection to the Internet.
2: From Google+.
If you have a Google Account you can quickly activate your Google+ account by going to Google+. Once you log in to Google Plus there is a Hangouts section on the right hand side of the page. To just chat, type your friend into the top Start Hangout box, and it’s the same as in Gmail. Click on Start Video Hangout on the bottom for Video. You can select who you want to invite and just wait for others to join. Or you can start by typing, then add video later.
There is a Hangouts page if you hover your cursor over HOME then click on Hangouts. This page shows you Hangouts that are currently in progress that you can join. Some of these are public, or if you select the Video Calls tab, you can see any Hangouts happening now that you have been invited to (or start your own).
3: From your phone.
You can download Hangouts for Android or iOS. If you’ve got an Android phone using Android KitKat, then you are likely using Hangouts for texting. To start a hangout, click the + in the top right corner. You can type a phone number (this is just texting somebody), name, Gmail address, or Google+ circle (the last two options will appear in their Gmail or Google+ window respectively if they are currently signed in). If they are not at the computer, they will receive a notification upon log in. The video button is on the top right to adjust to Video Hangout.
For all of these options, the max number of participants is 100 if you are chatting. Video chats have a max number of participants of 10.
Once you’ve done it once, it’s extremely easy to do it again. The bonus of using Hangouts is that it doesn’t matter what type of phone or computer your friend is using. If they have Gmail, then you can have a Hangout. Hangouts is also the only option that allows you to have up to 10 people involved in a Video chat.
To learn about different features once you are in a Hangout, check out my post Google Video Hangout Features.