Interesting. I've done text in many PBEM's but it never occurred to me to try a real-time chat game.
When I started playing on VTT, (OpenRPG for those keeping score at home), VoIP was still in its infancy and many of my players were on 56k modems or very early ADSL lines. Video was straight out, and we never bothered with voice chat. It was text all the way. Yeah, it was a bit slower, but, I did find that the role play was MUCH richer. People can stay in character in text much better than in voice. It really is a lot of fun playing that way. Very immersive. Particularly if you bolster it up with lots of images.
Anyway, back to my numbered list.
2. You can really lean on the computer to deal with a lot of the fiddly bits of D&D. Pretty much all the VTT's now have some sort of framework that handles the math and whatnot. Levelling up a character in Fantasy Grounds, for example, is as simple as dragging and dropping onto your character sheet. Very smooth. OTOH, VTT's do have a learning curve. They are not the most user friendly programs in the world and it can be a bit of a climb to learn how to do things using the program. Be prepared for a bit of frustration as you start out and have to fiddle around with the controls to make the program do what you want it to.
3. Participate in the game outside of game time. You're on the Internet, so, use it. If the DM has set up a forum (or is using someone else's) take a few minutes every week to post something. Background for your character, things you'd like to see in the game, that sort of thing. It will really energize your DM and make the game much better if he knows you're not just phoning it in for X hours per week.
4. It is very, very difficult to get feedback. The DM can't see you and it can be very hard to judge feelings over a voice chat. Private Message (or publicly if you like) the DM once in a while and tell him/her what you like about the game and try to give some constructive criticism. Again, the Golden Rule certainly applies, so, if you've got something to bitch about, do it politely with an open mind.
5. Presuming these are strangers, it's okay to walk away. Trying to get five or six people together on a regular basis to play a game that is primarily personality based can lead to lots, and lots of conflict. If you're not having fun with the game, walk away. No harm, no foul. You do not owe these people anything, nor, do they particularly owe you anything. Sticking it out will likely lead to frustration and even more conflict. There are a bajillion online games out there and everyone has different play styles. Just because you joined this one does not mean you have to stay with this one. Be polite and give lots of notice, but, if you're not having fun, walk. A politely worded email or message on the board is good enough. Thank the DM and everyone else for their time, and bow out. This is a good thing. You very well might have to shop around a few games to find a group that best fits. Again, there is no judgement implied at all with that. It's perfectly fine.
6. Be kind to the DM. By that, I mean don't test boundaries. If the DM says no X in the game, then, don't try to play X. Take the time to question the DM about what kind of game is going to be run, what are the expectations and what are the house rules. It's no fun getting surprised by something half way through play. Additionally, if you have rules issues, remember, this isn't a face to face game with friends. Make sure you know what you're talking about before you question mechanics. Take a minute to find page and paragraph and THEN bring up the rules question. It could be the DM is wrong, it could be you are wrong. Make sure you know what you're talking about first.
7. Before the game starts, take a minute to make sure your equipment works. If you have a five year old headset that you bought at the Dollar store, maybe it might be an idea to upgrade a bit and buy a decent headset and mic. Does your computer run the virtual tabletop AND the voice program AND maybe your web browser at the same time? Check it out. Most VTT's come with connection tests, so, again, make sure you can connect to servers before the game starts.
8. If you're going to be absent, make sure you
message the group and let them know. In this day and age of smart phones and whatnot, there is zero excuse barring catastrophe not to let the DM, at the very least, know that you can't make the next session. IOW, don't be a dick.

This is a social engagement and you should treat it as such.
Well, that's enough of my soapbox for now.
