selks - Gerund has given some very good generic advice, but there is one Nikon-specific thing you should do.
You should switch to 'RAW' capture.
To do this -
Press 'Menu'
From the shooting menu, find the 'image quality' setting and change it to 'NEF (RAW) + JPEG fine'
Once you've done this, whenever you take a shot it will be stored in both Nikon 'NEF' (i.e. raw) format and also JPEG format.
So why would you want to use RAW format?
Because it gives you a time machine!
A time machine Which lets you, from the comfort of your computer, go back and correct a number of parameters as if you were setting them on the camera at the time that you originally took the shot!
In particular -
- White balance - on the camera just set the white balance to 'Auto' and forget about it.
- Exposure - you can make exposure corrections of up to 2 stops either way - with absolutely no degradation. So for example you can take the shot with the camera up to 2 stops under-exposed, and still get a perfect picture on the computer. Obviously you should normally aim to get the exposure right, but if you don't, it's rarely a disaster.
- Picture controls - you can leave this on standard and change it on the computer later
- D-Lighting - again you can leave this on 'auto' and change it on the computer later.
Basically in the field you set all these controls to 'auto' or 'standard' and concentrate on your subject matter, composition and focus etc.
Then back at the computer you can do what you like with the exposure, white balance, saturation etc. Modifying these from a raw image gives a much better result than using (say) the photoshop 'brightness' slider on a JPEG image. You can use the free Nikon View software which came with your camera to do all this. The final stage is to export to JPEG format to publish your pictures, send to friends etc.
The only downside is that raw image files are much bigger than JPEGs, so you get fewer on your card - but you've got a huge card anyway.
Strictly speaking you don't need to keep the JPEG as well (i.e. set it to just 'NEF (RAW)' rather than 'NEF (RAW) + JPEG fine'), but I find the camera JPEG useful in the field for viewing on other devices (smartphones, tablets etc).