Movement and view
Movement is controlled with the joystick portion of the nunchuk. It is best to stagger your movement for a quick move to cover, and try not to shoot when on the run--movement will disrupt your aim in most situations. Use the crouch button and stay behind cover as much as you can when moving, as you want to present a minimal target to the opponent.
Your targeting reticle controls both where you are aiming and the viewpoint of your character. Move the reticle to the edges of the screen to look up and down or side to side. You can zoom in with the A-button for a closer view and should always use this when sniping or shooting at any range.
Ranged combat
The reticle-based aiming system is fairly standard, but the sensitivity of the Wii-mote means that even the slightest movement may be the difference between a head shot and a miss that alerts distant troops. Keep your arm braced on the edge of a chair or sofa so that this occurs as little as possible. Switch to your grenades or other weaponry outside of firefights when possible, as adjusting your hand to reach the directional pad will harm your aim. Due to this, grenades are often wildly inaccurate and are best kept for flushing out enemies that are dug in.
Bombs and melee attacks
The Wii makes use of interesting controls for explosives. You set the explosive with one motion and then rotate your Wii-mote to "twist" in the fuse. Pull back on the Wii-mote to activate the explosive and run. This process will completely ruin your ability to look around while setting explosives or provide any cover fire whatsoever. While this may be unintentionally realistic, it is best to ensure any areas are clear of enemies and your squad is there to cover you when working with explosives. Melee attacks generally consist of making a thrusting motion with the Wii-mote and nunchuk until your opponent can be finished off. You then use a side-to-side attack to finish the combat. There isn't much skill to this beyond button mashing--stab as much and as quickly as possible and finish your enemy quickly before support can arrive.