Question: I've noticed a lot of my pictures look muddy. They don't have very high contrast. I know I can post process some pictures, but what is the secret to having nice contrast in a picture?![alt text](https://i.stack.imgur.com/aDZWC.jpg)

Answer: 
Please, don't try to fix it later. Another teacher (where I teach photography too) says there should be no such thing as photo-correction, only photo-enhancement. Actually, I don't believe in the latter either ;)

You have to be able to produce sharp pictures with good clarity and plenty of details straight out of the camera.

If you are not, then hundreds of things can be wrong but without an example we cannot tell you what. Some of the most common problems:

* Camera shake: You have to be above a certain shutter-speed (depending on your lens' focal-length and whether it is stabilized) or use a GOOD tripod.
* Too high ISO: Cameras can reach very high-ISO nowadays but it does not mean they should, particularly small cameras with ISO above 1600 will make everything muddy. When lowering the ISO, take care not to use a too-slow shutter-speed though.
* Noise reduction: Some cameras have noise-reduction enabled by default which causes details to show up as muddy. Among small cameras, particularly those with a lot of megapixels (10+) you generally don't even have a choice.
* Out-of-focus: Your camera may tell you that things are in focus but it can still be wrong. If you are using an old-lens on a modern camera, this can happen quite a bit. Some high-end DSLRs allow you to correct this using 'focus micro-adjustments'.
* Your camera or lens is crappy: The biggest mistake when buying a DSLR is spending all your money on the camera and then buying the cheapest lens you can find. I'd say all modern DSLRs are quite good now, but not so of all lenses. Tiny camera with too many megapixels.
* Are you using flash? Pictures with harsh flash tend have a washed out look, with dark harsh shadows.
* In my experience non-SLRs (Point and Shoot / pocket cameras) get terrible results in-doors without a flash, even in situations that seem well lit to the human eye. Photos may look waxy from too much noise reduction (which is necessary in low light to get a steady shot, hand-held).
* A lot of the time the secret is to have good lighting in the first place. Sometimes a subject just won't look good no matter how good your camera is or how you set your camera settings, if the lighting is too harsh and shadowy. This can also happen in bright daylight, for example. The shadows show up black and the bright parts overexpose--- the camera may not be able to handle the dynamic range.