Oops, I dicoverde this thread just after my introduction in The Broken Drum, so I already replied to some of this questions there.
1. How did you come to read your first Discworld book?
A friend has borrowed it to me some years ago - regrettably I had to give it back.
2. What was your first Discworld book?
Thief of Time.
3. Will you read more?
Yes. And again and again.
4. Which one do you intend to read next?
Raising Steam, the last to read for the moment.
5. If you didn't start with Colour of Magic, how easily did you find it to get into Discworld? Did you feel that some background knowledge was necessary?
I don't really know. My friend was so enthusiastic that he right forward told me the best bits of discworld background which was needed to read this book, Death's granddaughter, Death of the rats and so on. It was somewhat confusing as the next books I read has been "Moving Pictures" and after this "Reaper Man". While reading this novel I wondered if the girl who appears here (wotshername?) may be the girl Death adopted and who later will become Susan's mother. Later I learned about Ysabelle and Mort, of course, but at this moment, yes, reading the books in the right order (at least the Death series) might have been a good idea.
Apart from that I get rather easily into Discworld, to read some of the books which I read first, it wasn't really necessary to know anything about "the disc" (for example "Monstrous Regiment", which still is one of my favourite books).
So, no, it wasn't difficult - if you get the personal relations of the protagonists right.