The personal touch really helps - and no, I don't mean memorise the names of all 400 pax, but when we're stretching our legs down the back on a long haul, it's nice to be able to just chat and have a joke with the crew (when they're not busy, of course). Helps us remember you're just real people the same as us. We might even share an interest other than getting to the destination in one peice!
Injecting a bit of humour in the announcements, including the safety briefing, if possible, really helps too. It makes people sit up and listen and not just see it as somthing you are doing to 'put a tick in the box'. From a VS flight: "Smoking is not permitted anywhere on the aircraft other than out on the wing, where the rule is, if you can light it, you can smoke it!"
One minor thing, I hate being called 'sir' and treated like I'm some kind of VIP. I'm not, and it actually has the opposite effect - making me think I'm just an item on a cheklist. (This applies not just on an a/c - also annoys me in banks etc.) Forced smiles and feigned politeness don't really work for me either, but I know you've gotta do it for everyone else, so I'm not complaining. I always feel really uncomfortable being told "goodbye" by a beamingly happy and perfectly presented crew member on disembarkation, knowing that (s)he's knackered and just wants to go to bed and never see another pax again!
For what it's worth, I've never felt the compulsion to complain about a member of cabin crew, and I do complain when I'm not happy, so you must be doing things right on the whole.
Well done, and T H A N K Y O U - (never really get chance to say that to your faces).