Mostly, I put some pretty ones in my reading space to look at.
I'll usually have my tiny turquoise Bhudda (Hotei, patron of fortune tellers) and more recently an opalite crystal skull on my reading cloth.
My 3rd crystal is a clear quartz that has been faceted to make the shape of a Hexagram/Merkabah (6 pointed star or Star of David). I think of this crystal as an amplifier for clear balanced communication and insight.
So aiding my readings.
Some of my decks have little crystals accompanying them inside their fabric pouches.
Chosen because I think they somehow match the "character" of the deck.
And sometimes I use crystals in ritual, in conjunction with Tarot cards.
On a recent thread about using Tarot for Halloween, I briefly described doing a ritual with a Tarot deck, and my 4 crystal skulls placed at the 4 quarters of my magic circle.
Will find the thread shortly...
Yes - here's what I said:
For Halloween night ritual:
I'll probably flip through my Barbara G Walker deck (Which is one of my decks specifically for ritual) draw some cards that speak of Samhain (Halloween) to me, decide what they represent and do a circle ritual to then meditate on these within it.
I happen to have some small crystal skulls - so I'm likely to use them to mark the quarters of the circle (Perfect!) - and then lay out cards near each one to see what the skulls have to tell me. This could be along the lines of "What do the 4 quarters have to say to me about balance through the dark half of this year".