Well, there is this little concrete pad off Goldenrod Rd. at the end of RWY 35. You can look straight down the runway. Also the Level 9 Parking Garage. You have to fill forms out though.
And then there is the Delta Air Cargo parking lot next to 17 that is really kind of off and on the airport. Be careful though as you might get chased out. As for spotting times, I would say in the early evening when all the Overseas flights come in. ( Virgin, British, MartinAir, and LTU)