Before you hop on the train, subway or bus:
Get into what I call the "early but relaxed" mindset.
If you think the the 8:15 train or bus will just get you to work just on time, resist the urge to take it. Instead, take one that gives you 15-20 minutes of wiggle room. Worst case scenario, you have some quiet time to enjoy in the morning or go for a short walk.
There's nothing worse than seeing the train or bus doors close as you wait for your ticket to print.
Have your work gear ready to go. If you want to check off some items off of your to-do list, make sure your laptop, iPad or phone battery is charged. If you need WiFi access, bring your own WiFi hot spot. It uses data from your cellular plan and converts it into Internet access. I have been able to file stories will on my way to and from work because of mine.
If you need to read a company report, print it out or download it to your computer before heading out.
Once you're on the train, bus or subway:
Don't be afraid to ask for (and take) the empty seat. Sure, you might be squished between two people or by the window, but you'll be relieving the congestion in the car and the stress on your legs.
Get that outlet. Is there a place to plug in your computer charger by the window seat? Try to sit near it or politely ask the person near the outlet if you could plug your charger in.
Seek out peace and quiet. Some trains have quiet cars, for example. I always avoid sitting directly in front of or next to a person chatting loudly on the phone.
(If you're in a quiet car on a train, don't be afraid to ask a conductor to politely ask loud passengers to keep it down. It's part of their job.)
If you need to catch up on sleep or relaxation, bring earplugs or sunglasses to block out distractions. But set an alarm to wake you up so you don't miss your stop, and make sure your phone's volume is on.