How to answer "Tell me about yourself" in a job interview?

I've got a job interview on Tuesday and I haven't had one for a while due to a period of unemployment because of family health issues.

One part of interviews I've always struggled with is when they first ask you to tell them about yourself. I struggle to talk about myself anyway and never know what they'd like me to actually say, whether it's about me as a person or about my work history.

So any tips or tricks would be welcome.