Originally Posted by abfab

Assuming you are flying BA:-

Firstly, if you have web access from 24 hours before your flight departure time, then it is really worth doing an Online Check-In on the BA website. That way you can choose your own seat on the plane, you can provide the Advance Passenger Information for US security, and therefore speed up your check-in at the airport.

If you have a printer, you can also print out your Boarding Pass.

When you get to T4, if you already have your Boarding Pass, then go straight to the "Fast Bag Drop" queue to drop off your luggage.

T4 doesn't have separate queues for each flight anymore, so you join one common Bag Drop queue which is for all the flights.

If you didn't print your Boarding Pass (or checked in online) before you get to T4, then when you arrive, you first goto a 'Self Service Check in' Kiosk to do your check-in or print your Boarding Pass. The machines are everywhere and should be easy to spot. There are staff available to help you if you have problems.
Then having done that, you go and join the common 'Fast Bag Drop' queue as above.

Once you have dropped your bags off, you are free to go though security which is half way along the check-in area.

Heathrow security can be extremely slow compared to BHX so make sure you allow yourself plenty of time to get though the system!