I have about a 50% hit rate for getting my units to harvest with a right-click.
Two things can be done to make it much easier:
1) polygon ray intersection for the clicking so we know you click on the visual representation of gold or a tree and not the tile that is some distance behind it but on that ray...
1b) or if you use colour-based picking, draw the resources onto the buffer too!
2) It would be very useful if, when right clicking a worker near a resource they can harvest, they harvest it even if you miss. The miss factor might be half-a-tile or one-tile - so very close, but not exact.
If the user wants to move their worker to that spot rather than harvest they can always use the actual 'move' command with the left-click destination.
Obviously (1b) and then (2) are perhaps much simpler to implement than (1). Anything to make it easier to command things.
