Allow plenty of time to get to the airport, motorway delays do happen. Think of arriving early as good manners to the check in staff, if you're late, they seem to take it personally for some reason.
Do know which terminal you are flying from, this is an excellent way to annoy the taxi driver.
Check in as soon as possible, don't wait for he queue to die down, with BA this will never happen. Heathrow terminal 4 can easily take an hour of queuing, I avoid BA whenever possible.
Request an isle seat, this allows you to get up for a stroll easily, and order drinks every time the stewardesses come nearby, and if you're worried about DVT (deep vein thrombosis) then the possibility of a saunter around is good for you. I always saunter towards the bar for some reason….
I'm a smoker, I delay going to the airside waiting area as long as possible, to allow for a good nicotine charge outdoors instead of a having to use a grubby, overcrowded smoking booth. (!!!?)
Flight departure monitors tell lies (usually). 'Boarding now' means in 30 minutes, until then you will be trapped in a non-smoking boarding lounge. Usually you're only allowed on the plane 15 - 20 minutes before take off. Providing that you have hold baggage they will give you a wake up announcement a few minutes before departure.
When you are on the plane, take note of your neighbours. If you're likely to be near noisy kids, or a passenger larger than the seat alongside, start panicking and look out for alternative spare seats, and then make dive for them as soon as the fasten seatbelt sign comes on.
Assuming that you are not flying BA, the stewardesses are probably human, be kind and chatty to them and you might get enough spirits forced upon you to make the flight pass reasonably pleasantly (if you are flying BA, hard luck!)
Duty free trolleys, usually a rip off, it's usually cheaper to buy when you've landed anyway, only pay in the national currency of the airline unless you want to be ripped off even more. Though they can be useful for getting rid of unwanted change when you leave somewhere on completion of contract.
When you land, the next stop is immigration, not normally a problem. If you require a visa you won't get in without one. They are a good way to get wound up before entering the country, only the British know how to queue, we are experts, all other nationalities realise that this is a waste of time and just force their way to the front anyway.
Nigeria is a wonderful country, (?) when the immigration gentleman demanded a 20 pound entry fee, I explained that I don't carry that sort of money and I had better go back home, so he let me in anyway. Hopefully you don't get too many of those problems. Try not to look like a football yob, or a mercenary and you shouldn't get any bother.
Customs, another wonderful bunch, hopefully looking out for drug smugglers, but in the UK seem more concerned with cigarette smugglers. I've had my car roof and door trim removed at Dover, and all I was doing was smuggling empty beer bottles back for my home brewing. If you want to avoid customs at Heathrow, fly in before 8:00am, I've never seen anyone on duty before then. I always try to fly via
Schipol or Paris, to buy as many cigarettes and tobacco as I can afford, Euro duty paid, as gifts for the wife, mother, father, brothers, etc. Keep the receipts and customs can't (shouldn't) bother you.
Airport taxis, I hate them, they've usually paid premium rates to get the airport concession, which of course they have to pass on to the punter by doubling the fare of a normal taxi. Once I've learned where to get to, I always do my utmost to bypass them somehow.
In Abu Dhabi the fare from the airport is AED 60, town taxi to the airport is AED 30, and the bus is AED 3, need I say more. From Thessalonika to Kavala, about 200 miles?? the drivers usually needed the fare in advance, so that they can rent a spare tyre, replace the treadless ones and fill the tank. (It might have changed in 20 years, but I doubt it!)
In Cairo, I walk far enough from the arrivals parking area, to flag down a city taxi who are delighted at getting a return fare.
Heathrow has the longest taxi rank in the world, about 1½ miles, it pays the cabbies to wait for up to 2 hours, to get a premium fare from some innocent (naive) traveller.
Air Malta - I can't forgive them for not serving alcohol on the flight from Tripoli, (Libya) after I'd built up a healthy thirst over a couple of months.
Air France - generally good, except one time they left me to sleep overnight in CDG airport during an air traffic controller's strike.
BA - I always get an old battleaxe stewardess or a raving poofta steward, (are they only reserved for cattle class?)
Gulf Air - I've got a soft spot for them, (sorry) they used to have attractive young stewardesses, working on contract, with an incentive to be nice, attentive, and keep me happy with a steady flow of miniatures. And the entertainment system always had the Goon Show in its repertoire, (Am I showing my age?) they now fly Airbus's which are falling apart after 5 years service.
KLM - good average, when flying to Hong Kong, a typhoon struck, we were diverted to Bangkok for a few days, and put up in a very reasonable hotel…..
Lufthansa, I've only flown club class, (sorry, har har!) where they serve as much whiskey as you need to pass the flight in a pleasantly comatose state.
Olympic Airways - they served the best in flight meal I've ever had, this was a long time ago and my judgement may have been clouded by having been in Greece for a year…
Thai Airways, see Lufthansa comments
Tunisian Airways - pleasantly surprised to have beer and vino forced upon me, without having to beg and grovel.
Turkish airways??? never tried them myself, but the wife wasn't impressed by the lack of seat belt, and what they claimed was food.