T's right -- use is required for trademark protection. Trademarks are labels by which goods/services are linked with their supplier. Think of Coca-Cola (which is descriptive, by the way) vs. Pepsi Cola. If you care which one you get, you're using the trademarks. If you don't care which you get, you're thinking generically.
Let's look at other possibilities for IP in a sentence or two. Bear in mind that I do patents, so I may be a bit "off" on the other topics.
Copyright: It's possible to have protectable rights there. You need to have enough "expression" to have protectable rights. You won't be able to get broad protection on the "idea" behind the expression. Of course, copyright people toss around "expression" and "idea" as if they're well-understood. I find the distinction a bit vague. Here's an example that's probably in the grey area. I've seen a sweatshirt with the text "Slower Minds Keep Right" in a design resembling a traffic sign. I've seen a T-shirt (which I believe to from a different source) with the same design but just slightly different text: "Slow Minds Keep To The Right". I have no idea whether they were independently created (a defense to copyright infringement) or who created first (also important in copyright). The idea is the same -- adapt a road sign to make a political message: particularly playing off the "slower traffic keep right" sign and the dual meanings of "right". The expression of that idea is different (perhaps reflecting different expressions of road signs in different regions). Now, how different is different enough? I don't know.
Patents: no dice. You're going need more than a sentence or two and much more than words before you can even begin to consder patent protection.
Trade secret: There are only two problems with trade secret protection for a clever quote. First, is has to be kept secret. That seems inherently incompatible with a "famous" quote. Second, it has to have commercial value. Your quote won't have commercial value if it's secret (I assume).
There are various other forms of intellectual property as well, but I don't think any apply.
As to how people get recognition for quotes, say a lot of clever things in public forums (and be famous for other reasons -- it can't hurt), and someone is bound to pick up a particularly clever thing you said and repeat it. Easy. ;-)
If you think your quotes might catch attention and bring you fame, there's a simple way to start selling stuff with your quotes on them --
www.cafepress.com. In fact, that's where I saw the sweatshirt (
http://tinyurl.com/9vnhy). I saw the T-shirt on Telegraph Ave. in Berkeley (no surprise there).
Regards.