There have been quite a few similar threads to this, but there are some good basic points that it doesn't hurt to bring up from time to time.
In my view, there are two things to bear in mind.
Firstly, there are the necessary crew announcements, usually at arrival and departure. If crew can get accross what they have to say in an individual (yes, witty is OK too) manner, then it makes even the most hardened SLF pay more attention. It also puts smiles on people's faces, meaning the passenger will have a good feeling about the flight and thus more likely to come back again.
The second thing is announcements during the flight. I am sure this must be taught in Flight crew 101, but the key thing here is to consider what the SLF are doing at the time. If it is in the middle of a movie, or when a lot of them are asleep, then announcements are simply unwelcome, whatever the nature and should be avoided, unless absolutely necessary. If a FA comes on the PA and wakes me up, or interrupts the climax of the latest blockbuster movie, to announce we will be landing in a little over an hour and this is the final opportunity to buy duty free, or that we are cruising at 36000ft and hope we have a pleasant flight, then frankly, they can shove it where the sun doesn't shine. The time to do that sort of thing is during meals, or other times when breaking concentration doesn't get people riled.