How to choose the best video calling method
But with video, there are too many variables. Which service will you use Which software Is the other person on my buddy list Are they online What if you want more than one person on the call Do all participants have sufficient bandwidth What if you want to share a screen And on and on. You can't "just" make a video call with a random person without thinking through these things.
Even with all those questions answered, technology might not cooperate. I used to have a regular video conference with two other people across the country using Skype, but more often than not, the connection was awful. After dropping and reestablishing the call a few times, we'd give up and switch to Google+ Hangouts, which behaved better for us. But in recent months, the opposite has happened repeatedly--Google+ Hangouts first drops video, then audio, and we end up switching to Skype, which has been weirdly reliable (given our history with the service).
As a result, sometimes I can't decide how to contact another person for a video call, even if the person is a Mac user with all the same software and account types I have. If you ever find yourself in the same boat, you may find my ruminations on the matter to be helpful.
Meet the contenders
As I mentioned in Replacing Messages Theater: more screen-sharing alternatives, there are oodles of choices when it comes to videoconferencing. I'm going to discuss just four: Apple's Messages and FaceTime (both of which are built into OS X and iOS), Google+ Hangouts, and Microsoft's Skype. These are among the most popular services, so it's likelier than not that anyone you want to contact by video uses at least one of them. Choosing a service for which the other participants already have an account is usually the path of least resistance.
You may well find a product or service that you and your colleagues find more reliable or easier to use than one of these four. If so, by all means, go with what works best for you--by mutual agreement, well before any particular call is scheduled. The start of a call (or the few minutes before it) is not the right time for someone to set up an account and become acquainted with new software.
Here are the key differentiating features you should be aware of:
Messages: The OS X version of the Messages app can use Apple's iMessage protocol for text and MMS messages, but for video calls or screen sharing, you must use an account type that supports video (namely, AIM, Jabber, or Google Talk). You can get free accounts for any or all of these services, and set them up in Messages > Preferences > Accounts.
Before starting a video call, you must put the other person on your buddy list--but you can add them unilaterally. Although you can have video calls with up to three other people, screen sharing is possible only when you're on a call with one other person. Note, also, that the iOS version of Messages does not support video calls; to use a service like Google Talk on your iOS device, you'll need a third-party app such as the free Vtok.
FaceTime: FaceTime, on either OS X or iOS, is great for one-on-one audio or video calls. Because it's simple to use and available almost anywhere, it's an ideal choice if you know the other person is an Apple user. And it offers highly secure end-to-end encryption. In most cases, you can use either an email address or telephone number to initiate a call, and the other party need not have FaceTime open or do anything special to log in. But you can't have more than two participants in a video call, and screen sharing isn't available.
Skype: With support for many platforms, multi-person video, and screen sharing (with simultaneous video), Skype is a great all-purpose choice for video calls, and it offers encryption (although with fewer protections than FaceTime). But it comes with a few gotchas. Before you can call someone, you may need their approval to add them as a contact (depending on their privacy settings). That's fine for friends and business colleagues, but if you're calling someone who doesn't recognize your name, there's no guarantee they'll accept you as a contact. Furthermore, the other party must be logged in to Skype on at least one device.
Google+ Hangouts: Like Skype, Google+ Hangouts can be used on a variety of platforms. On OS X, you log in to your Google account in a Web browser. All participants need a Google account as well as the Google Voice and Video Plugin (which you're prompted to install the first time you start or join a video call). iOS users need the free Hangouts app. Using Google+ Hangouts you can share your Mac's screen and have video calls with up to nine other people. If any of the other participants aren't signed in to Hangouts on at least one device, they'll receive a notification when you try to call them (which they may or may not see immediately).
A matter of protocol
What's the best way to choose among those options Your mileage may vary, but my own algorithm depends on the nature of the video call.
Scheduled calls: If you're planning recurring calls with your colleagues, the best advice I can give is to experiment, because what works for one pair of callers might fail for the next. Agree in advance that you'll use Skype for the first call, Google+ Hangouts for the next, and so on. Regardless of which service you choose for a given call, have a backup plan--if the call starts stuttering or stalling, all the participants should know which provider they'll switch to, or whether to try a conventional phone call.
Impromptu calls to a colleague: If I want to make an unscheduled video call to a colleague, my first step is to check the usual candidates to see if the person is online--Skype and Google+ Hangouts show participants's status, as does Messages for people in my Buddy List. (The status might be incorrect, but it's a good start.) If I can't ascertain a contact's online status with one of these services and I know the person is an Apple user, I try FaceTime. If none of those methods works, I use email, an instant message, or a phone call to see what works for the other person.
First-time video calls: First-time calls are the trickiest, because most people feel less comfortable chatting with strangers by video than in a phone call. If the person lists a certain service (such as Skype or AIM) on a business card, letterhead, or Web site, that's a fairly safe bet. Even so, the best idea is to give the other person a heads up first via email.