The personal welcome onboard after departure is one of the most important things to get right. It sets the mood for the flight.
As an e.g. On a trip LHR-LAX in C the CSD (Or whatever theyre called) came round and had a really nice chat with each pax. Asking if they were travelling for on holiday, recommending things to do, and where to eat etc.
Then a few weeks later on LAX-LHR again in C, i happened to get the same CSD but this time he just simply went around asking if we needed a landing card, and telling everyone to contact him if they needed anything.
Now i understand on the return trip crew are probably tired, but it showed me just what a difference it can make to the flight, in terms of setting the tone.