When you encounter friendly AI units, you can recruit and control them. The ArmA system for doing this can be quite confusing.
Recruiting unitsEditIf you have the difficulty set to display tags, when you encounter a friendly unit, the game will show a green tag that says Survivor. If you get close enough to them, you'll find an extra option on the action/mousewheel menu that says Recruit Unit. Select it and the friendly unit will join you. Down in the bottom left of the screen you'll see a couple of square boxes. The first one depicts you. The second (and any subsequent ones) depict the friendly units that you have recruited. If a friendly unit dies, their icon will disappear - it won't disappear immediately, but only once their death has been confirmed.
By default, recruited friendly units will follow you around. They will shoot at any hostile units and seek cover wherever possible. They're not the smartest cookies in the box, so don't be too surprised if they think lying down in the middle of a field is the best tactic for engaging a group of enemies. They will shoot at zombies and they will be attacked by them. They do not loot bodies or buildings (and there's no way to make them do this). They never run out of ammunition (they're programmed to have infinite ammo) although they do have to reload. They don't need to eat or drink and they don't suffer from the effects of radiation.
Issuing commandsEditThis is the bit that confuses most people. To issue an order to a unit, you first have to select it. Each unit has a function key (F key) that corresponds to it. You are F1, so the first AI unit is F2, the next would be F3 and so on. When you press the F key of a unit, you'll see their box light up to show they are selected. You can then issue an order in a number of ways. Look towards a particular location and you can order a unit to move there via the action/mousewheel menu.
You can also issue movement orders from the map. Again, select the unit with its F key and then just click on the area of the map you want them to go to, or you can use the mouswheel menu whilst hovering over a map location. If the friendly unit is in the driver's seat of a vehicle, they will use the vehicle to go there. Otherwise, they will move there on foot. Once they reach their destination, they will stop there and await further orders
You can tell them to attack a specific enemy by pointing at them or highlighting them on the map (if they're visible on it), but they'll attack all hostiles by default unless you tell them not to.
Controlling multiple unitsEditWhen you've got more than one friendly unit in your group, you can issue orders to them individually or as a group. As usual, press the F key of the unit you'd like to give an order. If you want to give orders to more than one unit, press each F key corresponding to the units. So if you've got three AI companions and you'd like to order all of them, press F2, F3 and F4 to select all of them. You then issue orders the same way that you would for a single unit.
You can give much more complex orders - splitting groups into different teams and giving different commands to them, but that's really beyond the scope of what you're likely to do in Ravage. There are plenty of online guides to ArmA commands if that's what you really want to do.
SpottingEditOne of the most useful aspects of recruiting friendly units is spotting. Whenever an enemy unit is spotted, the friendly will call it out. They'll generally give information about what they've seen, what direction it's in and the distance. This can be really helpful. Also, your character will call out the same sort of information. When you're on your own, your character never does this. But as soon as you've got a companion, your character suddenly gets very talkative. This is especially useful for things you haven't seen yourself.
The call will be displayed as text in the lower left of the screen as well as an audio message. Note that zombies will generally be referred to as 'unknown' units in the audio, but will tend to be called zombies in the text.
VehiclesEditWhen you're in a vehicle, you can order friendly units to get in and out. If you're in the driver's seat, they will occupy the other seats, including crewing weapons. Unless you specifically tell them not to, they will open fire on any hostile unit they see. As vehicle weapons cannot be reloaded (as of 0.1.34), you may find they burn through ammunition shooting at zombies, rather than saving it for hostile AI units.
Friendly units will happily drive and pilot vehicles whenever they have the chance. Be warned - they are not the most fantastic drivers and you may want to be careful before letting them at the controls of a valuable vehicle.
The AI is particularly bad at reacting to obstacles on roads. They will tend to follow roads whenever possible, but if there's a wreck in the middle of the road, they may well drive into it at full speed. This is something you can exploit with hostile units - when approaching a wreck, look out for vehicles that have crashed into it. You may well find a crashed vehicle with a dead crew inside, which makes for an excellent loot bonus as well as a vehicle that is usually easy to repair.
They're not always stupid, but they usually areEditWhilst the AI will do their best to follow your orders, they won't do it if they can't or if something unfortunate would result. For instance, if you're in a helicopter and you tell the passengers to dismount, they won't just jump out in mid-air; they'll wait until you land before getting out. This can be a useful way of chaining up orders during difficult situations. You can order a dismount whilst the vehicle is moving so you don't have the difficulty of trying to issue orders whilst trying to land.
Experiment with this in order to get a full idea of what they will and won't do. There are occasions when you'll get a unit stuck or they'll simply refuse to obey orders for no readily apparent reason.
There's a lot more to controlling AI units than is covered here. You can do some really complex things if you take the time to figure it out. Here's a video showing some of the more advanced options.