Generally, the rule I've heard the most is to have 2 workers per city if you are not industrious, or 1.5 if you are (one native worker and one foreign). And as Invisible Rhino said, the "mine green water brown" strategy often works. However, I sometimes irrigate grassland after I have get out of despotism. This allows for some 3 food tiles, and that allows for fast growth of cities. The rest of the grassland you can mine. And have roads, and eventually railroads, on every square that is worked.
Some cities will have a fairly large amount of hills and/or mountains. In these cases, you want to irrigate every flat square that will support it. Hills and mountains provide 3 shields every turn (out of despotism, that is

), which makes them good for industrial production, but won't do much good if you don't have people to work the squares.
As for the worker micromanagement, it will be tedious at first, but soon you'll find it results in more productive land. Or at least you'll get used to it after awhile and it won't bother you much anymore

.