If you know the commute ahead of time, I'd recommend booking at least 2 weeks out. It often ends up being cheaper than the average per ride cost with a 10 ride ticket. The 10 ride is also only good for 45 days at a time. Within 2 weeks, fares go up based on availability.

You'll want to check this and scroll down to restricted trains (http://www.amtrak.com/multi-ride-tickets). There are a handful of restricted trains and I'm not sure of what time of day those are. You can just cross reference on the NE Regional timetable. Also Acela trains aren't valid on the pass.

I don't use one but I believe on that route you still need to technically 'make a reservation' that will draw down your 10 trips. You can do it now on your phone or at the quick-trak machine at the station when you show up. Someone else can correct me if I'm wrong. I just do the purchase ahead of time method since I'm on a relatively set schedule.

If it's a long term commute, I'd also recommend joining Guest Rewards and getting the Amtrak credit card. The points are good for when you miss your intended train and can redeem those instead of paying the walk-up fare (assuming you don't go the 10 trip route). Shoot me a PM if you want a referral link.