well i expect others will chime in at some point, but for me, when i think of "casual"
i get and give (or expect to get)
sex (and it needs to be good, no point in having a sex thing otherwise)
affection and attention, but not too much, don't want a text every day
generally courteous behaviour, which really is down to what "i personally am" comfortable with (like I know I can't have casual sex with someone who is pushy or insists I come over to theirs at the last minute and isn't "nice" to deal with. I like the formal dating/seduction routine, it's all part of the foreplay for me. Had a casual night with someone on tuesday and he took me out before and offered to make me a cuppa and lift home in the morning)
i don't get (and don't want to give)
emotional reassurance or any promises of contact or commitment or them/me having to tell about plans or thoughts or deep feelings
any obligation or commitment - it can end after the 1st or 3rd or 6th night we have sex.
exclusivity, so they/i can/should be dating other people
goodnight anyway! 