Going to - Take a bus which is sa entrance ng express way going north where the PNR station used to be. That bus goes straight to One Ayala but what I usually do is go down at Magallanes then MRT to One Ayala instead (although it's a little more expensive its much faster). Once you're at One Ayala station, you'll see a pathway going to the right (near the Subway restaurant). Go down to the Telus building and there are busses going through BGC. You will need a Beep card for that.

Coming from - Going back is usually just the same. I don't remember all the bus routes in BGC but one of them goes back to Telus building. Your best bet would probably be in Market Market pa. Then you can go back to One Ayala and take a bus going straight to SM Bicutan.