Ride a plain Jane looking bike.
Take all easily removed items off and into work with you.
If you have a quick release seat post clamp bolt, remove the seat and seatpost too.
When you lock it up, park it between the two nicest bikes you can find on the rack.

If they want it they will get it. The game is to make your bike a PITA to steal and look like it's also not worth the effort.