I'll add some tips too
Go and get
IrfanView. It's free and in my opinion the quickest, no frills image editor/convertor that uses next to no resources.
Open IrfanView and press C. Select what options you want. I suggest:
* Foreground window (so you get just what's current - NO taskbar etc, more importantly if you use a multi-monitor set up it only takes a pic of one of them)
* Hot Key = Ctrl + F10 (So it doesn't do something like turn one engine off or go in slew mode in FS... I seem to get that all the time when multiplayer chatting ...)
* NO tick in include mouse cursor
* Save captured image as file with default file name (capure_date month year time etc)
* Choose destination directory - I have one entitled "Screen Grabs"
* Save as JPG format (although if I want a good quality screenie I often use Tiff which gives a 2meg file size, then convert to jpg later)
* Click 'Options' Change quality percentage to say 95%
* Press Start, it minimises to taskbar.
* Press CTRL + F10 to take your screenies.
You can use the program to crop them, resize, convert from and to 18 different file formats, sharpen, blur, and my favourite, batch convert/resize and rename many files all in one go. This is a must if you have 20 screenies you want to reduce to say 800 x 600 with a bit of sharpening and save as sequential file names.
Yell out if there's any queries.