When you don't know people well, it is advisable to avoid
certain subjects of conversation:
death, disease, religion, politics.
In British society certain questions are also considered presumptuous:
How much do you earn? Are you married? Why don't you have
children? How much do you weigh? The same goes for dates…
Topics such as your first three marriages, your biological clock or your carnal history may need to be covered at some point, but now is not the time.
Avoid rants and hostile debates and focus on similarities not differences. Keep your swearing count down and don't bother with too much self-deprecation.
Be cautious of too much humour. Jokes can wither and die in the face of incomprehension or be artificially applauded in the name of 'politeness'. Match your material to your audience: no matter how relaxed and easy-going your date seems, they may not appreciate a filthy gag that had you and your friends weeping with laughter.
As you get to know people better, you will feel able to stray into more challenging territory, but always do so judiciously: make sure you have a sympathetic audience or else you risk ruining a fine romance...