Whenever I have business in downtown Toronto, I will take the GO Train in from Aldershot station, the traffic chaos in Toronto is not worth it anymore. They recently (about a year or so ago) opened a parking lot on the south side of Aldershot station, and I have never had any trouble finding a parking spot there, even in the middle of the day! It is also convenient because most of the trains during the day travel on the track closest to the south parking lot, so that you don't have to take the stairs/tunnel to get to the appropriate track. There is a self service kiosk on the south side where you can buy a day pass. Trains to/from Toronto every half hour through out the entire day! Very convenient!

Ooops, I let my secret to abundant parking at Aldershot out! Darn! OK, don't go on the days I head into the city!!

To get to the south parking lot at Aldershot GO Station, take Waterdown Road south across the tracks (hang a right at the end of the ramp from the 403), and head east on Masonry Court, all the way to the end of the street. Parking lot will be straight ahead on the left. You can't miss it!

If I'm running late, I'll sometimes drive onward to Appleby GO station. The parking lot on the North side of the tracks always has parking available, especially with the new lot they recently opened up on the east end of the station (which isn't even shown on Google maps yet!!).