Photoshop users will recognise the brightness and contrast sliders, which are useful for more severe tweaks than the above controls, but unless you have Photoshop CS3, you may not be familiar with the Presence tools. These are now available in the Camera Raw module of Photoshop and need a little more explanation.
The Clarity slider is first and adds a edge contrast and sharpness to an image. Subtle use just adds a little snap to images, while more extreme use can really add a new element to a picture. Vibrance is another area that defies clear explanation; apart from it adds more vibrancy! According to Adobe it "adjusts the saturation so that clipping is minimized as colors approach full saturation, changing the saturation of all lower-saturated colors with less effect on the higher-saturated colors. Vibrance also prevents skin tones from becoming over saturated" and I can't give a better definition than that. The Saturation slider adjusts colour saturation from monochrome to full saturation. Play around with these controls to really give your images some individuality. For the effect below, I used 100 Clarity, 53 Vibrance and -51 Saturation, and boosted the contrast to 60.
The next panel contains a curve, similar to that in Photoshop. What's nice about this version though is that the sliders below control the curve, as well as the more traditional of click and drag. For beginners, this is a great way of learning how to use curves to adjust contrast and exposure as you can see how the curve and image change as you go. A drop-down menu also has three presets for quick contrast changes.
Colour is controlled by the next set in the chain. Changes to overall or individual colours can be made using Hue/Saturation and Luminance and the control sliders. General tips for these are to use orange and reds for skin tones, as the extreme sample here shows; greens and blues are the most useful for landscapes. A grayscale control is here too, also with colour controls for adjusting the tones of the original colours to adjust the monochrome grays of the new version. If you've ever used Channel Mixer for black and white conversions in Photoshop, you'll soon get the idea.