Rules that aren't really rules

Quick, tell me how many of you have struggled to avoid ending a sentence with a preposition? And by the same token how many have struggled to avoid using a conjunction to start a sentence.
Well, I am afraid, dear reader, you were dupped. Neither of these rules are really rules at all. In fact, they both stem from the Latin language. However, English derives more from Germanic languages than it does Romantic languges, so that's where we run into a problem. Let me guide you through why both are perfectly acceptable.

Ending sentences with prepositions

I once heard a joke about how two parties got along that goes something like this:
A couple from Georgia and a couple from the Northeast were seated side by side on an airplane.
The girl from Georgia, being friendly and all, said, “So, where y’all from?”
The Northeast girl said, “From a place where they know better than to use a preposition at the end of a sentence.”
The girl from Georgia sat quietly for a few moments and then replied: “So, where y’all from, bitch?” The original joke can be found here.
The idea is that ending a sentence with a preposition is somehow below the intellectual class, but I would argue it's only below people who fancy themselves to be the intellectual class.
See, in this case, the "where you all from?" isn't really a preposition. The "from" isn't actually a preposition, but a modifier to the verb "where".
Technically, such constructions are called adverbial particles, and the English language is on speaking terms with the construction. The Latin language called for all prepositions to fall before the noun, but like I said English plays more nicely with the German language than it ever did with Latin.
So next time someone tries to critique your use of a preposition at the end of the sentence, just ask them if they know what an adverbial particle is, and watch as that smug look falls from their face.

Starting sentences with a conjunction

We all know what conjunctions are thanks to time spent watching School House Rock (and if you haven't, you can just leave right now), but too many of us fear using one to start a sentence thanks to time under overzealous high school English teachers (by the way, if you still haven't left and still haven't seen the School House Rock video here it is).
Anyway, I am here to tell you that starting sentences with conjunctions is okay. No really, it's fine. I am not a high school teacher, so there's that to ease your fear.
I talked with my old high school teachers who forbade such activities, and they said they did so to keep students from creating sentence fragments because conjunctions can introduce independent or dependent clauses. The problem, though, is most younger students don't know the difference between the two, and so allowing a high school student to start a sentence with a conjunction may likely lead to a sentence fragment.
I figure most of use are beyond that point, so, really, there's no need to fear starting a sentence with an "and, but, or or" anymore.(In case you aren't beyond that point, here's a quick rundown of sentence fragments by my favorite English source, Purdue.)
Doing so actually creates extra emphasis that's required for such practices as persuasive speaking or writing.
So, in the hopes of casting off old chains, I suggest you go out and try writing a sentence with a conjunction as the first word. You'll feel better for doing so.