Let's see...

How to do taxes - Took accounting in High School. Yep.
How to write a CV - Sort of. Typically still look them up on Google to make sure I'm doing it right.
How to find a decent place to live - Questionable. I've never had an issue, but I also don't feel I know EVERYTHING to look for.
How to cook basic recipes - Put raw food in pan. Add cheese. Cook until not raw. Done.
How to understand the symbols on your washing machine - They seem pretty explicit to me...
How to unclog a drain - Poor in baking soda, add vinegar, plug drain, fill area with hot water, unplug drain and let hot water carry away all the junk. Works for most situations. Otherwise likely need to call a plumber cause the kid flushed a spoon again.
How to get over a hangover - Not sure. I hear eggs and electrolytes work. I know how to AVOID hangovers in the first place, so I've only ever gotten one.
How to find a GP - Where is this a hard thing to figure out?
How to apply for a visa - Not actually sure, I've never traveled to places where I've needed one.
How to register to vote - Check the box on my tax return. Super easy in Canada.

I'd say one very important thing that should be taught is how to research your local representatives. It's great that you've registered to vote, now you need to educate yourself so you don't vote for someone that wants to kill kittens. Doesn't matter what your ideology is, you should be looking into the record of your available candidates and make an informed voting decision based on your philosophy.

Best of luck on your book!