well first of if you have maya 8.5 and higher theres a physical sky and sun plugin in mental ray and that can produce good looking outdoor lighting, also it really depends on what look you are going for realistic (high noon, cloudy etc) or artistic. here are two links that can help you https://www.itchy-animation.co.uk/tutorials/light01.htm https://www.warpedspace.org/lightingT/part1.htm