Don't take up smoking
It's really bad for you. Meaning it might contribute to causing your death (and it is actaully quite likely). And death affects you most, but it affects hundreds of people who have met you in your life too. If it doesn't kill you, it can make you very ill instead.
It's expensive... £5 per pack, once a week is £250 per year. Can you afford that?
Will you be able to stop when you realise it was a bad idea?