I’m still pretty new to Quake Wars myself, but I have some beginner advice. Don't be afraid of the complexity: do what you know, and the rest will make sense later. Practice against bots, but don’t be afraid to play online and die a lot: you can still help your team, and you'll soon see your stats (tracked by Ranked servers) start to improve. 4newbies and BattleWiki are good reference sources to answer your questions, or search the official forums. GreasedScotsman’s tutorial videos are also helpful.
Meanwhile, here are two easy, non-complicated roles you can start with right away:
Best choice: play as a GDF Medic, and if you do the following you WILL be helping your team:
1. Look on your screen for a floating yellow diamond showing the direction to the current objective. If you don't see one, look at the sides of your screen for a little yellow arrow. Go there! If you can't survive in the heart of the fight, spend more time on the edges.
2. Hit 5 for defibrillators (3 gets your gun back).
3. Get up close to anyone--human OR Strogg--who is lying injured on the ground. Aim at them and click.
That's all it takes to help your team a lot. There's much more you can do (press 6 to be able to toss health packs around the battlefield--which you can even pick up yourself) but simply clicking with defibs does many things:
* Defibs on a fallen teammate revives them.
* Defibs (or any weapon) on a fallen enemy makes them impossible to revive (it may take more than one hit to make them stop moving).
* Defibs on a glowing red "spawn host" body destroys it--very useful. (Spawn hosts are a secondary way that Strogg can "revive.")
* But defibs on a body that's not "twitching" is useless--they’re already completely dead. Go for the moving bodies and the spawn hosts.
Second best choice: play as Strogg Infiltrator, with whatever weapon you prefer. (Railgun is powerful and zooms in more, but the trail gives away your location. Lacerator is weaker but fires multiple shots and won't give you away as much.)
1. Hit 5 twice for your Radar tool. Walk forward until you find a spot marked in all green, and click. Now your team can see enemies (red) on radar. (Hit 3 to get your gun back.) If you later find your radar is gone, just deploy it again.
2. Approach the battle (yellow diamond) and find an out-of-the way sniping spot.
3. Hit X to lie Prone (and spacebar to rise if you need to flee). Click the right mouse button to zoom in. Hit 'Use' to increase the zoom even more. Now you can see really well, but the enemy can't as easily see you.
4. Shoot enemies until they catch you! Anyone with a red triangle or no triangle. (White or green triangles are friends.) Aim for the head if possible. It's OK to shoot vehicles too--they're easier to hit!
That's it. Again, when you're ready, there's always more you can do. (Hold down 'Use' on an enemy body to disguise yourself, then sneak up to enemy deployables. Click to exit disguise, then aim at the deployable and hold down 'Use' to disable it. Remember, any time you have to hold down Use, hold it until the ring around your crosshair shows you’re done.)
Hopefully this is a helpful starting place if you’re intimidated as a newbie. Quake Wars is a great game. Have fun!
Meanwhile, here are two easy, non-complicated roles you can start with right away:

Best choice: play as a GDF Medic, and if you do the following you WILL be helping your team:
1. Look on your screen for a floating yellow diamond showing the direction to the current objective. If you don't see one, look at the sides of your screen for a little yellow arrow. Go there! If you can't survive in the heart of the fight, spend more time on the edges.
2. Hit 5 for defibrillators (3 gets your gun back).
3. Get up close to anyone--human OR Strogg--who is lying injured on the ground. Aim at them and click.
That's all it takes to help your team a lot. There's much more you can do (press 6 to be able to toss health packs around the battlefield--which you can even pick up yourself) but simply clicking with defibs does many things:
* Defibs on a fallen teammate revives them.
* Defibs (or any weapon) on a fallen enemy makes them impossible to revive (it may take more than one hit to make them stop moving).
* Defibs on a glowing red "spawn host" body destroys it--very useful. (Spawn hosts are a secondary way that Strogg can "revive.")
* But defibs on a body that's not "twitching" is useless--they’re already completely dead. Go for the moving bodies and the spawn hosts.

Second best choice: play as Strogg Infiltrator, with whatever weapon you prefer. (Railgun is powerful and zooms in more, but the trail gives away your location. Lacerator is weaker but fires multiple shots and won't give you away as much.)
1. Hit 5 twice for your Radar tool. Walk forward until you find a spot marked in all green, and click. Now your team can see enemies (red) on radar. (Hit 3 to get your gun back.) If you later find your radar is gone, just deploy it again.
2. Approach the battle (yellow diamond) and find an out-of-the way sniping spot.
3. Hit X to lie Prone (and spacebar to rise if you need to flee). Click the right mouse button to zoom in. Hit 'Use' to increase the zoom even more. Now you can see really well, but the enemy can't as easily see you.
4. Shoot enemies until they catch you! Anyone with a red triangle or no triangle. (White or green triangles are friends.) Aim for the head if possible. It's OK to shoot vehicles too--they're easier to hit!
That's it. Again, when you're ready, there's always more you can do. (Hold down 'Use' on an enemy body to disguise yourself, then sneak up to enemy deployables. Click to exit disguise, then aim at the deployable and hold down 'Use' to disable it. Remember, any time you have to hold down Use, hold it until the ring around your crosshair shows you’re done.)
Hopefully this is a helpful starting place if you’re intimidated as a newbie. Quake Wars is a great game. Have fun!