Does my camera shoot in JPEG or RAW?
If you use a normal "point & shoot" camera or a mobile phone, then your camera will shoot in the JPEG format. There are higher end point & shoot cameras that can shoot photos in RAW, however unless you have explicently changed the setting, it will be in JPEG mode by default.
Digital SLR cameras will allow you to shoot in either format. If you're unsure which format your camera is shooting in, it is most likely in JPEG mode.
I can fit more/less photos on my memory card than your calcultor says. Is something wrong?
This calculator gives a guide to how many photos you will fit. Not all photos take up the same amount of space, thus sometimes you may get more or fewer photos on your memory card.
What size memory card should I get?
There is no right answer to this as it will depend on your own individual requirements. For normal people, 8GB will be enough for most evens (birthdy parties, weddings, etc). If you're shooting in the RAW format, then you should look at 16GB as a minimum these days as memory cards are cheap!
Should I pay more for a high speed card?
If you're shooting with a point & shoot camera, probably not. Class 6 speed cards or higher should be fine.
If you're shooting with an SLR, especially one that can take many photos per second, a high speed card is a worthwhile investment. (Class 10 or faster).
How many megapixels is my camera?
Most point and shoot cameras will have a label on the body of the camera with the answer to this question. Otherwise it will be on the box or in the manual that came with your camera.