cruise control (atleast on my 92 525i) is the lever below the wipers...push forward to set, pull back to reduce speed, and i never have used the up/down part yet...so i'm not quite sure what they do...
as for the buttons by the clock...each one is unique, it can tell you the temp, time, date, avg mpg, range left on the tank, avg speed, stop clock, est. time of arrival, distance counter...lots of cool stuff, theres also one on the bottom right that I can never get to work but you can set a 4 digit code for ignition, get it wrong to many times and you cant start the car, unless you pull the battery...