Although a wealth of information can be mined from census, birth and death certificates, and other documentation, these often leave gaps over which we can only surmise. I've talked already about the gap in my father's life between him leaving Scotland and arriving in London. What we seekers of family knowledge often forget to do is speak to our actual family.
My father always said he wished he'd listened more to the women speaking (his mother and aunts) at family gatherings. I now find myself in a similar position, wishing I'd asked my parents more. Now they are both dead, I can only go on memories and letters. I thankfully have one living link remaining - my mum's cousin, Pat - and this year I have put that connection to good use through letters and phone calls. This has answered several questions for me but raised others.
Remember to talk to your family while you have them.