At the beginning of the game, I always order my settlers venturing out to build a city to construct roads on used tiles; this way, I can parry financial shortfall after I have built eight temples <IMG SRC="http://forums.civfanatics.com/ubb/smile.gif" border=0> In addition, mining on hill tiles is essential if I really want the Colossus/Hanging Gardens in time.
As for other tile improvements, I wait until eight-fifteen cities have been built before I start irrigating and mining in earnest. The AI, however, starts doing this right away, which is why its expansion is at a snail's pace. 'K' automates settlers; be warned: what it will start to do may frighten you! It will wander aimlessly, build irrigation on an unused tile, and enter enemy territory. It does, nevertheless, have a useful advantage: it can irrigate without rivers/coast. Perfect if you constantly get unlucky like myself!
However, I hate miromanaging settlers/engineers. CTP's "public works" feature fixed this, but took away a strategic element in the game. Better have a faster, less taxing way to automate settlers ...
[This message has been edited by bvd (edited July 19, 2001).]