Northfield is the main track I play, I bet every race I watch live and bet ahead for most of the races before I leave.
If it was just one of several tracks I played there would be only two types of bets that I made.
Several races a night (on most nights) there are two or three fairly obvious exactas. With the condition sheet sometimes there are horses that are two seconds faster than the rest. If there are three horses that are better, with the drivers colony the way it is out there, two of them can get into a speed duel and mess everything up.
The other race I would bet is the 9th race pick 3, if a less than even money favorite wins the 8th race.