For the first flight: window or aisle is a matter of personal preference, just avoid middle seats.
If you pick an aisle seat, take it in the central section: that reduces the number of times you may have to let your neighbour through by a factor of 4.
Pick a seat in a set if 3 where one is already booked: that will leave only a middle seat, which is usually not favoured, so may remain empty. The further back you are the best chances of this working (but if you are in a hurry take the front most seat you can find).
For the second flight: a middle seat is miserable in any case, but in the central section at least:
- you won’t be bothered by your neighbour in the window seat wanting to get up: both your neighbours have aisle seats and get access the aisle directly;
- You have two different choices of a neighbour to bother to get up.
In terms of row, there are two things to consider:
- if you are in a hurry at your destination it’s better to be closer to the front, as that can save you a few precious minutes;
- if you are towards the end of the meal service you will have less choices, but it can be difficult to guess in what order service is performed. They usually start from the galleys, but sometimes the service pattern is different. You can override this if you order a specific meal in advance.
There are overhead lockers for your carry-on, though they can be quite full in coach (though usually less than in single aisle aircraft). You want to avoid keeping stuff under the seat in front of you: you want that space for your legs and feet! Note also that one some aircraft, some or all seats will have a box under each seat for the IFE (in-flight entertainment, the screen in front of you) which will already reduce your space.