Let's say I want to promote the great-tasting pizza at my new restaurant in Bitburger, Arkansas.
1. Assuming no one else has used it, can I trademark the phrase, "Bitburger's best-tasting pizza"?
2. Even if I cannot trademark that phrase, can I still legally use the phrase with a TM after it, in order to ward off would-be competitors?
One thing to note is that by asking "can I trademark", I understand that you are asking whether or not you could obtain registration of the mark through the US Patent/Trademark Office (e.g., get that magic ®). That understanding of your question will be used in part of this answer. (Another thing to note is I'm not a TM guru so my reply here is based on having had a couple of classes and the fact that I Slept In A Holiday Inn Express Last Night. So don't take it as gospel or as legal advice - just general info.)
1. Probably could not obtain federal registration. The suggested phrase is essentially a description of the geographic location of your pizza shack along with a bit of descriptive puffery. The problem is that phrases that just describe the product are not generally fit for registration. The idea being that society does not think it is appropriate for an individual (you) to be able to take general, descriptive words that have been used in the public domain, and monopolistically yank them back out of the public domain. Another issue you would find with trying to get federal registration is that marks must be used in interstate commerce. Is it likely that a small town pizza joint will be doing interstate commerce?
2. This is another kettle of fish and the answer will vary from state-to-state because now you're in the area of common law trademark. In my own state, I can pretty much use anything I want as a mark and indicate such with "TM" (assumes as you've stated, no prior users in the same field). But my own state's laws are pretty similar to the federal registration guidelines such that "Anytown, USA's Best-Tasting Pizza" would be afforded very little in the way of protection. That is, if I start selling product under this name and next month someone copies it, it may be tough to enforce because the mark is just a descriptive phrase. Maybe it's different in Arkansas and Kansas, though.