(Warning, incoming wall o'text detected)

OK, so I've said a lot of stuff, and it's all just my opinion based on my own experiences. If you find another way that works for you, that's the one you should use.

Well, the typical situation would be that your group all gathers round at someone's (usually the DM's, but not always) house, and you all sit round a big table.

There's a map in the middle that everyone can see, and the DM has a little corner/end of the table sectioned off by the DM Screen which conceals all of the detailed notes that you can't allow the players to see. This would usually include a map of your own, which will be smaller in scale, but far more detailed.

I realise this won't be quite the set-up that you'll have, as you've said you're getting the group together virtually, but you should be able to work on a variation of it.

Your secret map should contain all of the information that you need to run the encounter: a full layout of the building/cave network/forest clearing/whatever that the players are exploring, with starting positions for all the monsters/creatures/NPCs, and the positions of any traps/treasure/items of interest. Next to that you're going to want some notes about the area. If it's a particularly important/impressive area you might want to start with a brief paragraph giving a description of the place. Your notes should also contain quick references for any rolls that might need to occur, for example a list of the DC ratings for Perception Checks to spot any traps. I also tend to have a separate sheet for all adversary combat stats (starting Hit Points, AC, Attack Rolls + Damage, etc.) - you can just refer to the page(s) of the Monster Manual, but if you've got a bunch of different creatures then you're going to be forever flicking back and forth.
You'll also want a space somewhere (again, I tend to use a separate sheet) for recording the Initiative Order, and the current health of monsters.

In comparison, the map available to your players should really only contain the information that would be available to their characters (but is a lot more than just a blank grid). For example, your map may show that they are in a room, with a corridor leading off it, and two ogres waiting just the other side of the door, ready to bash the head in of the first person to open the door. The players' map will show that they are in a room, with a closed door at the far end. Your notes may then have the DC check required for the players to hear the ogres before they open the door.

Theoretically, the players' map should only cover information that their characters know, so in the case of a room with closed doors there shouldn't be any lines beyond them until the players open the door, and then you can reveal the room/corridor/whatever. In practise, this will slow the encounter down a lot, and mean that you are constantly re-drawing things. The more practical solution is to map the full layout of the area, but only as far as things like walls and doors go. Internal detail, such as monsters, weird symbols on the floor, sacrificial alters, the bones of a previous adventuring group, etc. will only be added once someone can draw line of sight to them.

Also, if you've got a big area that you want them to explore, don't be afraid to split it up into several sections, and separate maps for each section.

Also also, most of the powers/abilities that the characters will have will be given a range measured in grid squares. If you're running a combat/puzzle encounter (really any encounter other than a conversation/social interaction), then it will be necessary to keep track of where everyone is. This isn't true for every game system, but I think it's very true for D&D 4th Ed.

So, how to adapt all that to your situation?

Well, if your group is going to be a mix of those physically present in front of you and those virtually present, then you'll want the big player's map.

But for those that will be present virtually, however many that is, you need to find a way to get the map information to them. Players only really have two ways of receiving information about the situation their characters are in: what you tell them, and what the map shows them.

You're still going to want to have two maps: one for them and one for you, but if they are all going to be virtual presences keeping your one secret won't be much of a challenge.

The difficulty is going to be in getting the players' map to them. There is 'virtual tabletop' software available that will allow you to do this. I believe some of them are even available for free. However, I have never used any of them, so I can't tell you exactly how they work or how good they are.

My group has used a couple of techniques before, which worked (although not as well as just getting everyone together).

The first is that the DM sets up a physical table, with a webcam pointed at it. The players can ask for the viewpoint to be moved during their turn, and tell the DM where they want to move to (move my paladin 3 paces forward and 1 to the right). The DM is basically in charge of the board, and moves things at the request of the players. This has the advantage of being unambiguous - if you see the DM moving your piece different to how you intended, you can correct them (or correct yourself if you said the wrong thing), and everyone is looking at exactly the same thing. The downside of this is bandwidth/connection quality - it may or may not be practical for you all.

The other option is that the DM prepares the players' map(s) in advance, either drawing them out by hand or sketching on computer, and e-mails them out to the players. If you've got several maps you'll have to give them titles so that your players will know which ones to refer to (and make sure you don't give anything away with the title - no point in naming it 'Goblin Ambush', even if that is a nice summary of the intended encounter). You'll also need to give actual grid-references, so that you all have a common point of reference for the map. Each individual is then responsible for updating the position of all characters/monsters/etc. on their own map. The advantage of this is that it can be co-ordinated via audio only, there's no need to set up an additional webcam and work out how to get it aimed at the game board properly. The disadvantage is that your games inevitably turn into some weird hybrid of D&D and Battleships, which can make co-ordinated tactics like distractions and flanking manoeuvres more tricky than they need to be. As the DM, it will also be your responsibility to resolve any issues that occur as a result of people being in the wrong place.

One thing you will have to watch out for is making sure that everyone gets to have a say in discussions. This was a bigger problem in my group, because we've generally only had one person gaming remotely - and it was very easy for the group around the table to forget about, or talk over, our not-so-absent friend (on one memorable occasion our DM that was the one virtual person, and two of the players got into an argument with each other about something that the DM was trying to clarify, but they were ignoring him because he couldn't turn his speakers up, whereas they could just talk louder to drown out the 'distraction').

Making sure that they get their fair share of time in combat is easy enough - the initiate mechanic basically forces it, but if you get a few people together chances are one of them will be a little quieter than the others. My advice is to work out who this is, and then try and listen out for them: if the group is having a big discussion and they don't seem to be part of it, specifically ask them for their opinion on the matter.

Seeing as this topic is about drop off the front page, my e-mail address is samurai_ireland@hotmail.com - if you have any more questions you can contact me there.

- Irish