Getting an iChat account through AOL instant Messenger
This assumes you don’t have a a mobileme (previously known as .mac) account which is another way to activate iChat.
Configuring iChat for Google Talk
This allows you to do googletalk instant messaging using iChat. Unfortunately iChat’s voice, video, and screensharing capabilities do not work with googletalk but you can activate googletalk voice and video using Gmail as described in the next section.
Gmail Voice and Video Chat
Installing this software supplements instant messaging with your gmail contacts with the ability to also do a voice and video chat. If you don’t yet have a Gmail account, here is How to Register for Gmail (step by step) or How to Register for Gmail (the video).
Screen Sharing with Windows or having Online Meetings
After configuring and installing the software described you should be well on your way in using iChat and Google Talk for instant messaging, voice calls, and voice with video calls. In a separate post I will provide information on how to do screen sharing for presentations, support, collaboration etc. between different computer types. If both people have Macs, just use iChat through your AIM or mobileme account but if you want to collaborate with people using Windows or you want to have a meeting with more than one person it gets a little more complicated.