The most important data you need to either look up (in digital photography the camera is recording it for you) or put down in a note book (refers more to manually controlled film photography) is: ISO, f-stop (how widely open is the aperture in your lens?), shutter speed and focal length.
So you may have taken a photo at 35mm (focal length), at ISO 200, f 8.0 and 1/125sec. Which, in case you focused well, ought to be sharp even on your computer screen, i.e. when you see the LARGE version of your picture (in the tiny screen of your camera almost every photo looks just about "good", since it is sooo small, all that went wrong cannot be seen that size).