I have fished Cochituate for trout mostly in the North pond. But to really fish Cochituate you need a boat. Be advised that especially in the north pond there are some questionable characters that frequent the area. Also on the advise of the dude with the white beard and the bike you want to avoid bringing beery beverages on your trip. EPOs like to confiscate the beverages or pour them out if they catch you fishing with them.
For trout the best times to fish this water is early in the morning.
The North pond is on the right and the Center pond is on the left off of route 30 heading west.