Depends on when and where, I have used KY, and men's cum /precum, and when things are real tough spit. LOL
If I am at my house then I use elbow grease. I love it,it feels all tingly at first and lasts a long time. If I am somewhere there isnt any then my own juices plus his precum usually does the trick,if there is nothing else better.
I get very wet so only ever used my pussy juices
If with a male partner don't really need extra lube.
But if alone or with a female partner and using toys/strap on always keep some KY or Astroglide handy