I don't mean to sound rude, but I would submit that the problem really lies with you. The students feel that you're the type of person who will accomodate these behaviours. I would suggest at the start of your next class, lay out the rules and adhere to them. Those who wish to play their own reindeer games can do it elsewhere, and if they don't receive a high enough mark. Oh well...
With all due respect, I think this is incorrect.
I teach college as well. This bs happens no matter what kind of teacher you are. If you are strict, the bs does settle down a little bit, but you can't fight every single battle every day. Well, not if you want to last more than one semester. And even after most of it settles down, you're still left with piles of it anyway.
I honestly don't care if students are eating in class as long as they are still paying attention and they're not making any gross noises or leaving a mess. I am clear about this from the start.
For the other stuff about assignments and sloppy work - yup, that's how it is these days. And yes, I hand back work ungraded if it's not to my standard. Crappy work is rewarded with a low or failing grade (depending on how crappy). I just handed back two failing grades last night without a qualm. Oh, make that three. One student plagiarized. In my classes, the first time someone plagiarizes, I talk to them and see how they react. If they get immediately embarrassed, I usually give them another chance. They still fail that paper, but if they are good for the rest of the semester, I'll give them a chance to rewrite it. If the student, however, tries to deny it, then they get a 0 for the paper, and they are warned that the next little hint of the same will result in failing the class and being reported to the college. I can give you a long list of students who have failed my classes and been reported to the college.
But here's the thing.
They always try. They always start out trying to get away with sloppy work, disrespectful behavior, and attitude. It takes most of them several weeks to really get the hint that they shouldn't f*** around if they want to pass my class. Some of them finally get it and start improving. Others finally get it and withdraw. Still others don't ever get it and end up with an F.
There's only so much you can do. I might win the battle of the cell phones and the double-spaced typed essays with correct heading (THAT takes at least half the semester) and no-extensions, no-late-papers, but I have to accept the fact that some of them will always forget to capitalize their names, some will always leave at least one 'u' instead of 'you' in an essay, some will always come in late... These are not the ones that are getting the good grades in class, mind you, but they are at least doing the rest of their work and they have a good enough attitude in class participation to pass the class.
I give very few A grades, and in almost 10 years of teaching at this college, I've only been asked about grades a handful of times, almost all of them about why they 'only' got a B+ instead of an A. "Because you earned a B+" is always my response. "But I was there every day and worked really hard!" is their argument. "So did the C student who sat next to you. I'm not grading your attendance and effort. I'm grading your performance." That's usually the end of the discussion.
OP, may I offer some suggestions? Don't smile for the first month of class. It's much much easier to be a dick at the beginning and then loosen up a little later on after they already respect your rules. It's impossible to go the opposite way, however.