If you just rely on your eyes, it will be very hard to know if the lane is oily or dry. The reason is that the oil used in bowling lanes are clear and invisible to the human eye. The best way to know is by observation. You can see from the rings on your ball once it comes back to you from the lane. The lane is dry if you see an earlier hook on your ball than usual. The lane is oily if you see a delayed hook.