To "case a joint" is to check out the details to, and make speculations about, a home, car, store or other location for means of getting in undetected and/or removing material from said location.
Usually referred to negatively as a means to describe being suspicious someone is going to steal someone's belongings, it can also simply be a synonym for reconnaissance.
1. That banger over there was casing the joint when I came in this morning.
2. Tell Tommy to go case the Sanders' joint and see if Paulie's car is there.
3. I saw you going out to case a joint earlier, you better not take anything.
12 step recovery jargon referring to someone new who talks about how great life is, now that they'resober. Usually meaning that the person is out of touch with reality.
The new guy seems pretty happy for a dude who has no job, no money and no family. He must be on a pink cloud.