Prone
In my opinion this is only really useful for ambushes and sniping. Whilst prone you may be a smaller target to those level with you but anyone above sees your full length. Also you stick out too easily if you move due to Half-Life being unable to deal with it properly.
The bonus with being prone though is that almost all recoil is removed except for MGs and automatic weapons still have some spread but you don't have to fight to keep the cross-hair in place any more.
Going prone is also a good way to sneak past enemies when you have a low wall to cover you, dod_anzio is a good example the bridge is best crossed prone or at a sprint. If you're sniping prone is definitely the position of choice and weapons like the Garand and Carbine definitely work better whilst prone, it's just a matter of point and click.
German Leicht Infanterie with stick grenade
Voice comms
Unless you've actually played with a clan at some stage voice comms are probably a little alien to you. At the moment in DOD they are used mostly for random comments on the public servers. But occasionally it is used properly and then the game really works. Why should you have to type every message when you can just speak it? It's faster and easier to take action if you're surprised whilst speaking than typing. I have been caught typing a number of times and you end up writing a message along the lines of "Enemy ahead tawasda." You always try to move before you realise that you're typing instead and in that time you're usually dead.
By using voice comms as well you can more easily keep the whole team aware of your location and intentions and issuing orders is far faster, with the others giving real time feedback. There's no need with voice comms to skip any smaller messages because you can't be bothered to type. The only downside is messages can be garbled and you'll need to configure it properly to get the best results. Also everyone comes out sounding Irish or Scottish for some reason, unless maybe only the Irish and Scots are using it?
Also if you start issuing orders they will generally be followed. No-one else is generally willing to take a tactical role in the game so if you start telling the team to all attack the left flank most of them will. DOD players seem to want leadership but on public servers there is very little. All it needs are some motivational rants to "Take the last flag now!", or "Rush them before they reform" and this collection of random players will suddenly become your team, especially if what you say leads to victory.