T spots can be competitive to get. There are only a few of them and a lot of people like to busk. You should either grab a spot first thing in the morning or plan to go in the afternoon for when the early buskers leave.
If you’re going in the morning, trial and error is the only way to learn. Start by showing up at 10:00am at a spot and see if it works. If not, you can adjust from there.
Part 3 of my How To Busk in Boston series is now up. This is the most direct and exciting article since it discusses the first busking session. Click on the link to get the whole article.