I must admit I have the worst of all bad telephone manners - I don't answer calls.
Ever since the first day I got a mobile day I have permanently left my phone on vibration mode. Don't know why but I absolutely hate my phone making a sound. The result - I always miss calls, a lot of calls.
As one of my self-imposed, crazy, nonsensical, Monkish and annoying to everyone but myself rules that I adhere to religiously, I don't answer calls when I'm having a conservation, in a restaurant (any restaurants, be it McDonald's or one in the Michelin), or traveling in a bus, MTR, ferry or whatever means of public transport. Incoming calls are intrusive. I hate being intruded and avoid intruding into people's life. The Blackberry/Android/I-Phone have come to my rescue. I can sms/whatsApp first to confirm it is OK to call. And I can tell people they should sms/WhatsApp/email me instead of calling me. Love it. Great.