I try to buy a mix of hard/medium/soft, cow/goat/sheep, at least one blue of some kind, to have a contrast of tastes and textures. Then assorted biscuits, oatcakes, grapes, dried fruit (pref apricots or figs), nuts (pref walnuts), a chutney or pickle of some kind, some quince cheese (membrillo), a dish of cornichons, and celery sticks!!
I would also say better to have bigger wedges and fewer cheeses rather than loads of smaller bits - it looks more generous.
For instance the last cheeseboard we had:
Brilliat-Savarin (soft, cow)
Ticklemore (medium, goat)
Barkham Blue (blue, cow)
Manchego (hard, sheep)
Or you can do:
Cheddar (hard, cow)
Chevre (soft, goat)
Ossau-Iraty (medium, sheep)
Stilton (blue)