I live in north centeral Nevada and i just baught a OMNI Directional scanner outdoor antenna and im lookin for the best direction,and height, to put it for the best coverage and signal.
An omni-directional antenna receives just about equally in all directions, so it doesn't matter which direction you face it. As for height, usually the higher the better.
Put it as high as you reasonably can in a location that has a clear path in all directions if possible.
You don't want to go to unreasonable lengths to get it up high and end up with excessively long coax runs where the coax loss will offset the gains of the extra height. Obviously, this is somewhat of a balancing of factors and is made less of a problem is you use better coax which has less loss per foot.
You can find a coax calculator at this website which will let you play with different options.