Park at the Boston Common Garage and either take the train or walk. It’s typically a breeze getting in there and it’s only $16 evenings/weekends. But it’s Boston so there’s always a chance you could be sitting in bumper-to-bumper. In that case the safest way is to pretty much hit up the closest train station to where you live and hop colors. The reason why I park under the Common is because I don’t like the trains and I have no idea how late I’ll be in the city. I’ve come very close to missing the last of the trains and having to Uber all the way back to Alewife.