We take the conkers out of their green cases, Ally, so they are like the brown conkers you use in the children's game.
Convention says place one conker in each corner of the room, but we leave nothing to chance, there's flippin' conkers everywhere. Just be careful you don't step on them, though - painful!
We also have a wooden fruit bowl full of them as a seasonal autumnal display on the hearth (just in case spiders come down the chimney as well
). We usually add acorns and pine cones into the display - acorns are no problem this year but pine cones are more problematic as I usually pick them up down Poole or Bournemouth way, where the flora is more heath and gorse, but we're not going out on trips like that this year.
We probably picked up at least 50 conkers last week, shiny ones, plus around 20 acorns. Good luck to your Sis!