How Does One Get Rid of Unwanted Houseguests?

I find myself asking myself that question lately. So what do I do? I turn to the all-knowing oracle that is Google.

I found this. It has some good and hilarious tips.

And this. A little more tongue-in-cheek.

And this, which gives some good advice but is geared more to a specific type of houseguest.

Hmmm, I need something more specific. Not answering the phone/being at home when said person wants to stay is of course a good option (though tiring if they do it EVERY WEEK), but what about those times when said person drops by uninvited during the day, because they have nothing else to do and just want to park their ass on your couch for awhile? That's what I have more trouble with.

Somehow, if you ask that sort of person to leave, they always complain loudly that you don't like/want their company (duh) and they're not that horrible. Then they get in a snit, which of course sometimes has the desired effect of making them leave, but it would be better not to have to go through it all in the first place.

I tried Googling "How to discourage people from dropping by unexpectedly" and didn't get anything that I could use. I could not answer the door, but if said person sees my car and knows I'm home, it will just create more problems. I need to clean out the garage so I can fit my car in there. And get curtains for the window. :-D

I've tried parking elsewhere, but I get nervous about my car and panic when I hear the doorbell anyway. I could make sure I'm not home, but then I have to stay away all day for at least a week, maybe more. Where will I go? I like staying home. And I don't want to feel like I have to run away.

In my ideal world, I would live on a nice hidden acreage/farm outside the city, unknown to said person (which could be difficult, as said person is my mother). But oh, I dream about it!