When you disagree about approach, don't debate; choose one person's approach
(preferably the most junior of the pair) and try it out. If they're wrong,
reality will prove it. If they're right, you just learned something.
See also: Llewelyn Falco's "Strong style pairing" article (linked above), in
the "Ask for trust" section near the end.
Attribution in version control
Update your git config so both pairs' names appear in the git log.
git config --global user.name "Alex B. and Sarah L."
At regular intervals (<30 minutes), switch roles with your partner. Set a
timer, but don't be dogmatic — if the navigator is just about to
finish a thought, let them do so.
A version control commit is a natural time to have someone
else take control: you may find it helpful to work in small chunks that can
be started and finished in 20-30 minutes.
Attend to your personal needs
You can get up and leave whenever you want, without offering an explanation.
Consider using Pomodoros: 25 minutes of work, 3 minutes off.
Unless you firmly establish this as your policy, you are likely to "power
through" when you feel you need a break because of some imagined social
expectation — you'll end up needlessly tired and ineffective.
When you take your turn at the keyboard, take a moment to place it fully in
front of you (instead of leaning awkwardly out of your seat).
Consider each others' personal space: make sure there's enough room where
you're sitting that you're not right on top of each other (coughing and
sweating on each other)
Consider keeping a bottle of hand sanitizer to use when handing off the
Chat about what is and isn't working; adjust to suit.