Greetings:
Vicar-style. Best done on a sit-up-and-beg style bike, like a
Pashley Roadster Classic. Heads up, remove hand from handlebar, wave heartily in the air and say in a very clear voice "Good Morning Mrs Timpleworth. Lovely day". (Assuming that I have failed to offend Mrs Timpleworth, as I don't think that there are any). Variations on this are acceptable, but should stick to the same basic pattern - no first names, no modern transatlantic greetings, and nothing more controversial than the weather.
Friendly-neighbour style. Suitable for any flat-barred bike, but preferably of the touring/classic style. Remove hand from handlebar, offer it stationary in the direction of your target greetee, and state "Hiya", "Hello", "Morning", "How do" or "Alright" depending on where in the country you are.
Hybrid style. Suitable for the modern "hybrid" bike. Don't remove hand from handlebar, but use head or finger so acknowledge presence. Same verbal greeting as above. Hopefully you are travelling fast enough for the words used to be arbitrary.
Road Bike with or without lycra, but without club gear. At the friendly end (no lycra), a finger wave with one hand is used. For the cooler approach (obligatory whilst wearing lycra), just a quick nod or tilt of the head. No words.
Road bike, full lycra, club kit, head down, or tourer with steel frame, Carradice saddle bag, leather bidon. Nose almost imperceptibly raised in the air. All words muttered under breath or in head only.
Full suspension mountain bike bought for less than £80: "f*** o** you b****** s*** for b****. Come here and I'll k*** your f****** h*** in." Accepted response is "S*** the f*** up or I'll g** an A*** on you."