Hmmmm, I'll just throw out some things.
- Try and get the technology out of the way early. In other words make sure your players have FG installed, and that they have successfully connected to you (as a test) before the scheduled game time. This can be done days early of course, and the players don't need to connect simultaneously, they can do the test when they get the chance. This also establishes that you have all of the correct ports open on your network.
- The same thing will apply to voice chat if it's being used. Make sure everyone has it set up and working before the scheduled game time. If you aren't using voice chat, you might want to keep it in mind as you play your first sessions. Some people like it for internet gaming, some don't.
- If you have a set group of gamers that are going to be playing, you might want to run a free FG module to start with. This will provide you with a preprogrammed adventure, and also give you and your players a chance to get used to internet gaming. I know it's tempting to jump right into a campaign, but I think it's better to take a couple sessions to get comfortable with the method and program you all are using to play. Of all my suggestions I think this is the most important. Just take it easy for the first couple sessions.
- Online gaming can actually be pretty fast. Some people say there's fewer distractions playing this way (and leaving out voice chat can make the distractions even less), depending on typing speed of course. A lot can depend though on the DM's preparation, since a prepared module will have any lengthy descriptions all ready for dragging over to chat, all the NPC's prepared, and maps made. Just like in RL, those things can be done on the fly, but they'll take a little longer than if they are prepared.
- Be mentally prepared for technology issues, and don't let them rattle you.
- The legendary "anonymity" of the internet is very beneficial for internet games. Your players may actually be more in character than they've ever been.
Internet gaming is still in it's infancy, but it's going to continue to grow and get better and better. I think even now it's a great option for long distance campaigns with friends that have moved away, and I expect that it will become more so as the programs that facilitate it become better and better.