Can't get the monitor to work while composing shots

Poolseman is correct that most DSLR cameras do not feature a 'live view' on the lcd. Light does not hit the sensor until you release the shutter and take an exposure. When you remove the lens you will see a mirror which relects light up through the pentaprism (an interesting piece of glass that flips and reverses the image and sends it out through the viewfinder for you to see). Most of the sound you hear when shooting is that mirror snapping up and out of the way to reveal light to the sensor (CCD in your case). If you took a long exposure like 10seconds, you cannont see through the viewfinder because the mirror is not reflecting. All SLRs work this way. However, a few of the latest Canon SLRs from this year DO support a live view of whats in front of the lens. I'm not aware of any other bodies available that can do this, but if Canon is doing it, its possible, and probably will turn up in other brands later this year or next year. If you're trying to take a shot above your head etc and cannot see what you are doing, I submit that practice will tell you how much area the lens is getting and what angle to estimate. In a case like this the lcd might not help much anyway since they do not view well at extreme angles. Hope this helps...

Because your camera is a digital SLR you cannot ( physically impossible ) preview 'live' images prior to the shutter being released . The reason is that the device generating the image viz. CCD sensor is behind a CLOSED shutter so it 'sees ' nothing and hence thre is no picture available to be displayed on the monitor. It is only when you activate the shutter that the CCD sensor can come on line and capture/generate an image which is available always only after you shoot.