Signing In and Out
Note that except when specified otherwise, all pieces of paper referenced in this article are assumed to be located at the RLO.
Also note that these rules can often be fudged a bit, but you should try to avoid doing so more than necessary.
Since you don't have Four to Six or Eight O'Clock sign-in on the weekends, you're supposed to sign out when you go to food at the Union or Station. This involves signing your name or initials on yet another piece of paper along with the time, and writing the time again upon return. This is probably one of the most commonly bypassed sign-ins because it's easy to walk out the back door without thinking about it. You may get written up if an RC sees you, but I wouldn't worry about it as long as you can honestly say you'd forgotten (or can execute a passable lie to the same effect).
If a large group is going somewhere, there is usually a group signout sheet. You sign up on that sheet, and then sign back in when you return. Pretty simple. It just saves them the hastle of shuffling a bunch of yellow cards at once.
This is a card all your own, and it is used in most situations where the above aren't available. If you are leaving campus, leaving Cooper after 8pm on weeknights or for just about anything other than meals on a weekend, you're going to have to sign your yellow card.
Some people have been known to get away with not signing out under these circumstances and others have been known to receive no slack at all. While you can experiment to see which category you fall under, a useful catch-all destination is "Walking".
You'll enter an expected time of return. If you don't want people coming to look for you, try not to overshoot it by too far.
This is another card all your own, and it's more or less identical to the yellow card. You get to sign this if you're planning on leaving campus for at least one night. In general, this means closed weekends and holidays.
Now, this is also the card you sign if someone comes to pick you up (and take you away from campus for at least a night). In such a situation, they have to have been explicitly permitted by your parents to do so, and must be at least 21 if they're not taking you to your house.
For additional policies, consult your MASMC handbook.