We each put forward three suggestions, on a bit of paper with a short description of each book. Then we all discussed each person's suggestions and decided what to read. That was successful.
Next time we chose several genres of book - classic, poetry, a play, a chicklit, an (auto)biography, a science fantasy and a book not originally written in English. Each of us drew a 'genre' out of a hat, then compiled a shortlist of 3 suggestions as above. This was not so successful as researching the suggestions was quite hardwork.
Finally, we all suggested a book we had read and loved, and everyone else read it.
The books which provoked most debate and interest were 'Veronika decides to Die', 'The Time Traveller's Wife' and 'Fortune's Rocks'.
We met at each other's houses, we all knew each other well and there was absolutely no pressure at all to provide lavish food. Some did - their choice, others (like me!) laid out snacks from LIDL.
Lots of wine was drunk and at Christmas we did a Secret Santa, with books as gifts, of course!
I absolutely loved my book group and missed it once we had disbanded (amicably, by the way)