Generally I have the found that the amount of time I spend monitoring a manager's progress on a task is a function of my familiarity with and faith in that particular manager and in the importance of the task. With the top-notch performers, they know the level of business issues I want to be involved in and they know not to bother me with smaller issues. They also know that I'm not real happy if certain higher level decisions are made without consulting me.
It boils down to: a) my trust in the manager, and b) my sense that the manager has a good grasp of the level of authority he/she is free to run with. I'd prefer to be hands-off, but for new managers that I don't know well, or for those venturing into new or certain critical areas, I may spend more time than usual in informal chats about how things are going.
"Trust but verify"
As a GM you are totally responsible, so how can you totally delegate? You must "trust but verify," as Ronald Reagan said. You need to keep your hand in the cookie jar. Every day the Wall Street Journal has articles on big management fiascoes where top management didn't know what was going on. They were so busy with the view from the balcony that they didn't watch the store.
I went to a HBS reunion seminar several years ago where the emphasis was on the boss "following an order" through the company to see how customers are treated. It's a great idea and it works. I have over 2000 customers but I want to make sure my employees are treating them right. I train them and give them my corporate philosophy; but I also check up to be sure that the customers needs are being met. Whenever possible, I spend time talking to customers even to the extent of pumping gas on our gas dock. That's where I learn more about our customers' needs than sitting in my office.