Or simply the way session zero is done?
I give a lot of explanations to new players and to people that come to our Friday Night Dungeons. People know that I am a harsh DM that challenges the players to do their best and perform above and beyond normal expectations. Pushing their limits and so on.
I also tell people that short rests is a full night sleep and a long rest is a full week in a safe environment such as an inn, a castle or stronghold. Anything else only gives a short rest and you can only have two short rest between long rests. Not 3, 4, 5, or 6. Only two. So you'd better be wary, prudent and aware of the consequences. I also modified the light cantrip. It now only gives the light of a candle. I enforce the disadvantage rule on perception check without light so people carry torches and one of the great magical item can have is actually the Drift Globe. Players love that magical item and want to have more than one at all time!