I wrote these out for a client who wanted help improving her staff's photography at work. They are very simple tips but a few people seem to have found them useful so I thought I'd stick them up here.
1. Don't always use flash. Leaving flash on its default setting means the camera will almost always activate the flash, even when your shot would look much better in softer, natural light. That's because most cameras will take an average light reading from the entire frame, without taking into account the lighting on a specific subject or the light effect you want. Common instances are with sunset shots (where auto flash will just highlight possibly ugly details in the foreground), food shots (nothing looks more unappetising than a plate of food lit by an auto camera flash), building interiors and details, plants and portraits. Remember that with the flash deactivated a camera on auto settings might want to keep the shutter open for longer to let in more light, so practice holding the camera steady or use a tripod to avoid a blurry image. If you've got steady hands you should be able to keep a sharp image at shutter speeds of 1/30 of a second or even slower. If there's still not enough light then also consider increasing your camera's ISO sensitivity (see below). 9 times out of 10 auto flash will completely kill the atmosphere of a shot, so only use it when you really need to. This is a really simple way to dramatically improve your photography.
2. Use your ISO settings. ISO is a really useful and easy to use tool, but most people don't take full advantage of it. Increasing your camera's ISO setting makes its digital sensor more sensitive to light, so it 'soaks up' light faster. This means the camera's shutter (which lets in light) doesn't need to be open for so long, so blurry images caused by camera shake are less likely to occur. Increasing the ISO setting is a great alternative to using flash if you want to keep an object's natural light and maintain the atmosphere and colour of a shot. The thing to remember about ISO is that the higher the setting, the more 'noise' (graininess and loss of detail) will appear on the final image. Most digital compact cameras will give you usable images up to around 400 or 800 ISO, depending on the quality of the camera. If you're not too fussy about image grain, or if your camera is a high end model, then you can consider using ISO settings of up to 1600. You'll be surprised how much difference changing the ISO can make - it allows you to shoot in much lower light than normal. Remember to return the ISO settings back to default (100 or 200 ISO) when there is adequate light to ensure the best image quality.
3. Move. The place where you're standing when you first see a shot is very rarely the place you need to be when you take it. The human eye will automatically isolate the subject of interest and ignore background clutter, while a camera will capture everything regardless of what's of most interest. Get closer to the subject to limit background clutter, and try to compose your shot so unwanted distractions are out of the frame. This might sound obvious but it's amazing what can spoil an otherwise good photo if you're not paying attention. Shots taken from the default 'straight-on, eye-level' position often lack impact, so consider all your options; can you get higher or lower, or shoot from another side? Most importantly remember to consider where the light is coming from. If the source of light (the sun, for instance) is behind your subject then you will be shooting into it, and the subject may appear dark. A good rule of thumb - though by no means obligatory - is to keep the light source behind your own back so it's lighting the subject. Changing your angle of view can dramatically improve your final shot.
4. Keep it simple. Be selective with your choice of shot. Be fussy. When photographing large, complex scenes such as places, buildings or events, just shooting the entire scene is not always the best way to capture it. Quite often there are interesting subjects within that scene which will make a better final image and more effectively convey a 'sense of place'. For instance, if you are shooting a crowded market don't just take a 'wide' shot and move on. Instead try to find a subject within the scene - an interesting face or a colourful stall perhaps - which gives a more personal impression of the place. Trying to include too much in a shot often dilutes the impact of the final image, while concentrating on a particular detail will result in a much more pleasing photograph that gives the viewer a more intimate idea of what it was like to be there.
5. Break the rules! The great thing about digital photography is that taking a photo doesn't cost a thing, so don't be afraid to blaze away and be creative. Tips such as 'don't shoot into the sun', 'keep the horizon level' and 'don't crop out part of the subject' are useful tools to bear in mind, but don't let them inhibit you if your instinct wants to take over. People who spend all their time getting a shot technically 'perfect' - following all the rules and messing around with tripods, light meters and an array of different lenses etc - very often end up with very boring, sterile shots lacking in any originality or atmosphere. So don't be afraid to experiment. Go ahead and shoot into the sun - you'll get interesting lens flare and silhouettes. Get super close to a subject and fill the frame with it - who cares if half of it's cropped out? If you want to fit more of the subject in the frame, don't be afraid to tilt the camera off the horizontal - if the horizon behind is tilted it will only give the shot more punch. Rules and tips are great for avoiding 'problem shots' and helping you capture what you see, but for truly creative, individual images you have and go with your instincts.