Hi Pat , as you know you can view your seats at any time , and at -72 ( to flight time ) other seats get released , that are held for status , and then everyone can do the OLCI , ( on line check in ) at 24 hours before flight .
Normal check in procedures like others , and you can choose to print off your boarding cards or collect at airport etc etc . We always go to the desks which are in Zone A in the North Terminal ( to the left as you enter ) and drop off bags and also collect a boarding card ( and then keep our printed ones we do at home as a back up ) we also have a mobile boarding card too !!! There's no way I'm not going to get on that plane !!! And then just through security .
You can do your own boarding card and do bag drop , but the desks are not really busy and I've never seen big queues ever , so it's just easier to do a normal checkin at the airport , but by doing the OLCI , you've secured your seats .
If you do end up with 2 or 3 types of boarding cards , just use one type through the airport journey , so use the same one at the departure gate as you used at the beginning of the security check .
I'm sure everything will work out fine , if you do manage to get on the MMB at -72 just look at the airline type , at this moment it will just say 777 , at -72 it will say so something like 77A or 77S , which will be the series and registration of the plane , which will narrow down the plane registration you will very likely to be flying on
It's at the top of the page when you expand the flight details and have the option to click " view or change seats "
Good luck and enjoy your flights .