Last time I went, there was a woman in the herd who was called the name of a film star. The bloke in charge of calling out the gangs of twelve really loved being able to call out "Joe Bloggs; Jack Miggins; Debbie Reynolds!" It lightened up our otherwise tedious day.
Definitely take a book or two - or your phoney-thing so you can wave your hand around and play patience.
Apart from that, just do with the flow. If you get the chance, be the chairman of the jury. It only involves sitting there looking wise and inviting assorted oddbods to suggest various angles. Of course, it is then you who has to stand up in court and declare your verdict in front of a crowd of the acused relations, or whatever.