Ideally, the camera should be fixed to a tripod but any solid surface will do. You can zoom the lens and compose the image, remember to allow space if you plan to join one end of the group. Most of the time the camera will autofocus and give the correct exposure. Sometimes it is better to switch to manual focus (if available) and adjust the lens before you press the shutter button – this makes sure that the focus is on the most important part of the scene.
The problem with using the self-timer for group shots is that you can’t control when the picture is taken. People either anticipate the exposure and have fixed smiles, or they are taken by surprise.
Some Canon EOS cameras have a built-in infrared receiver that operates with the Canon remote control unit RC-6. You can aim the unit at the front of the camera and press the button to fire the shutter. Aim and press the button, then move your hand down to hide the unit before the picture is taken. Two seconds later a photo is taken.
The short delay givers people less time for a fixed smile and you can fire when everyone is ready.