Ok, when changing strings, you are never going to want to use the whole length of the string - I doubt if it would even fit on most tuning pegs. YOu want about two or three full winds around a tuning peg, any less and the string might slip, any more and you can get tuning problems, especially on a tremelo equipped guitar, as the winds take slack in odd ways.
The height adjustment saddles are generally set pretty well in the factory, but sometimes they aren't.. The lower the height of the strings, the easier the guitar is to play (unless you play slide). However, if the strings get too low they start to buzz when you play them at certain frets, as the vibrating string touches against the next fret up from the one you are touching. You can play around with the height yourself to see what you like, but record the height that they were originally at. If you want to get the best out of the action (action is what string height is called) of your guitar, send it to a guitar to get it "set up". A set up will normally include action adjustment, truss rod adjustment, intonation, fret clean, and a new set of strings.