There are 3 different modes which you may use to shoot stills on the Nokia 808.
The first being Auto mode which as the name suggest every settings is controlled by the phone itself except for the flashlight keeping things as simple as possible.
The second mode is Scenes. In this mode you are able to choose between various scene types namely, Landscape, Auto, Close-up, Portrait, Sports, Night, Night Portrait, Spotlight and Snow.
The last but definitely not least mode is the Creative mode. This mode offers full control over a huge range of settings. Exposure, White Balance, ISO, Neutral Density Filter, Focus mode (infinity, hyperfocal, close-up and automatic), Colour tones, Capture modes (bracketing, interval, self-timer), Saturation, Contrast and Sharpness. Besides, Creative mode also lets you choose between full resolution and 3 levels of PureView mode (8MP, 5MP and 3MP). Your settings can be stored as 3 different pre-sets for quick use in the future.

ISO is one of three settings used to control exposure. The other 2 being f/stop value and shutter speed which in this case is not available for adjustment manually. An increase in ISO simply increases the sensitivity of the sensor to light. However by increasing the sensitivity in light, noise level will increase alongside.

White balance is the process of removing unrealistic color casts, so that objects which appear white in person are rendered white in your photo. The unrealistic color cast is caused by the difference in light source. A candle light for example casts orange shades onto your image requiring the adjustment of white balance to ensure that white-coloured objects appear white in your photo. Basically, it is like a calibration tool to recalibrate the colour tempereature of your camera.

Focus mode is used to control the focal distance. Infinity is basically used when the subject that needs to be in focus is far off. Your camera will focus on the furthest possible distance. As far as I know, Hyperfocal will result in the same reult as using Infinity focus. Hyperfocal simply means objects that are beyond the furthest possible focus distance achieved by your camera in Infinity mode. Close-up would obviously be used when shooting Close-up requiring a short focal distance and Automatic being automatic.

Contrast in the imaging is the difference between the lights and the darks. If you have a picture that has little contrast, its usually very subdued. If you take an picture and turn down the contrast, the light parts of the pic become darker, and the dark parts become lighter. If you turn it up, the opposite happens. Generally speaking, turning up the contrast makes the subject stand out a bit from the background. Its not always, but generally.

Saturation is the amount of a color. Increasing saturation sort of purifies that color and brings it out, makes it stand out potentially. Decreasing it draws that color out of it. Desaturating generally means removing all the color altogether.

Anyway, a few quick tips to shoot good photos.
(1) Rules of thirds usually works great. The rule of thirds is an imaginary tic-tac-toe board is drawn across an image to break it into nine equal squares. The four points where these lines intersect are strongest focal points. The lines themselves are the second strongest focal points.
(2) Photos are always better shot with proper lighting. Ensure you have the best possible lighting while shooting the subject to obtain a best possible image.
(3) Different angle produces different results. Try it out and obtain the best possible angle.
(4) Experiment all you can. Take a million photos if you need. Practice makes perfect.