Hooyaah: Never forget your mother and/or special someone on their birthday.
Never assume that a generic person's mother isn't abusive.
In general, never assume things about generic people, as any such assumption might not hold for a specific person.
KiNgBrAdLeY7: Never spend money on DRMed products
Never assume that a product can't be DRMed because it's a piece of hardware.
(There've been reports of DRM or artificial restrictions in devices like printers, refrigerators, and even cars.)
Also, never connect something vital that could be used for nefarious purposes to the internet. In particular, devices like thermostats should not have an internet connection.
Oh, and if you're ever in charge of an election, never do vote by computer.
KiNgBrAdLeY7: Never unveil your first and foremost priorities, true aims, real goals.
I disagree with this one.
On the other hand, I can say:
Never say the opposite of what you mean. (In particular, never use sarcasm.)
DavidOrion93: Never drink a can of beer in a church.
Never play hopscotch on crosswalk intersection.
Never assume anything about a generic church; how do you know the church doesn't have services that revolve around beer? How do you know the church doesn't host activities where alcohol is served?
Also, for the hopscotch thing, there are events like block parties and some holiday celebrations where the roads are closed down.