...and I was just wondering if anybody has any starting tips for me?
It's the first time I'll have had my mits on a DSLR - bar holding one in the shop.
Are there any quirks of this particular camera that I'd benefit from knowing about? Any great tips in general?
I just have the standard kit lens that is normally sold with these cameras - so any tips with that would be great.
Also - ISO - what the hell is that all about? Can someone point me in the directions of some fab, easy to read links or summarise the important bits for me?
I'm beyond excited, I wish it were Wednesday already!!
From someone who has to, erm, 'put up' with one, let me give you a few tips. (Its a love/hate relationship with my 450D...

)
The autofocus system on mine, a friend's and another friend's isn't all that good. I've concluded that generally to folk with an eye for detail, the 450D's AF system is probably a bit shoddy. I get around this by simply using manual focus, or contrast-detect autofocus in Live View. This is the same, ridiculously slow method that compacts use, but it gives pin sharp results. And I mean
pin sharp.
If you are going to use the quick autofocus, I would advise you use centre point only. It has extra sensitivity at F/2.8 too, and if you let the camera decide where to focus, it doesn't always get it right.
Try not to use ISO 1600. Ever. It's a noise fest of completely and utterly noisy images, and the amount of noise removal required to get rid of noise will just ruin the image. In exceptional circumstances (flash helps, or if the light isn't diabolical) you _can_ get away with ISO 1600. Noise actually starts to creep in at ISO 800 and in some circumstances is even very slightly visible at 400. Generally speaking with mine I try to compromise ISO last; and I find 200/400 generally my best bet. With a really fast lens like the 50 f/1.8 you might as well drop it to 100 in daylight.
If you're wondering what ISO is, it's just a sensitivity scale. back in the days of film, different rolls would have a different ISO number and this denoted how sensitive it was. ISO 200 for instance is twice as sensitive as ISO 100, meaning it needs only half the amount of time the shutter is open, to give the same exposure. High ISO on digital makes noisy images because the signal from the sensor is simply amplified, meaning any noise is also amplified.
When you're taking photographs try to avoid F/22 - that's when the aperture of the lens is really small, and can, allegedly, cause diffraction. In laymens terms that means a poorer quality image. Also, to get well exposed images when the aperture is that small, you need good light or a really slow shutter speed, or high ISO. Some lenses are also quite soft wide open (low F/ number, with the aperture open as far as it will go) so avoid wide open as well unless you need it in low light or you want max depth of field effects.
On modern lenses the aperture does not open and close correspondingly to you changing its value on screen - it simply closes to the selected value when the shutter fires. To 'preview' what it will look like in your viewfinder, press the DOF preview button on your camera, which is just to the top left of the '450D' logo. This actually closes the aperture blades to the value you have set, thus darkening the VF slightly and showing the actual image that the sensor will see (except for exposure as this depends on how long the shutter is open for). If you have a nifty fifty, look into the aperture as you press the DOF preview and you'll see the aperture fins close to the specified value.
To turn on focusing in live view, see the custom functions menus. Make sure to turn on 'contrast detect' focus and not the quick focus for best results.
Finally, the pop up flash doesn't work well with lenses wider than about 17mm, but it makes a great 'fill in' flash. This is when your settings are ample to expose the background, but your foreground (maybe a person's face?) needs a bit of light throwing onto it to complete the picture.
Here is an example of a fill in flash that I used to throw light onto the intended subject:
Also, have a think about rule of thirds. This is easy to accomplish with live view on the camera because it has lines on the screen which help you compose the subject. Rule of thirds basically involves offsetting your subject to a 'third' of the frame of the image to give it a nice, aesthetically pleasing look. Here is an example... *shameless plug*
Rather than just sticking the valve in the middle of the image, which would make it look lifeless, i put it at the bottom and left the top fairly plain with as much bokeh as that lens could handle.