Being a "demanding jerk" is a surefire way to lose respect from the students. Be firm with your expectations but also understanding when they don't meet them. This doesn't mean they can get away with not meeting the expectations, but it does mean that you understand that kids are humans too and have good days and bad days. You also need to be "authentic". Be yourself. I'm weird and goofy. I'm also a nerd and don't take myself too seriously. I embrace this and display it in front of the kids and they in turn respect that and respect. That doesn't mean they all like me, but they do what I ask with little push back. When a kid does push back I reinforce the expectation and give an appropriate consequence. I don't get mad, and I definitely don't take it personally. Remember, "respect" shouldn't mean "fear". Respect isn't gained from anger or being a tyrant. Also, don't confuse being "like" with being "respected". This is a problem that a lot of young teachers (and most classroom teachers) have. Think about how coaches get respect from their players. Do the same thing. This may sound sacrilegious, but we are basically the same as coaches when it comes to building relationships with our students. Treat them with appropriate respect and they will do the same. Be true to your expectations and fair and honest with the kids. They will come around. It won't happen overnight, but work at it and it will happen.