Camel: Really focus on getting the momentum when you go into the spin. Keep your arm level on the wind-up, and swing it around (without dropping it) as you go into the spin. My coach told me to pretend I was sweeping a bunch of plates off a table with my arm, and my camel spin has been my best element ever since then. Try not to drag your free leg on the ice as you enter the spin because that will slow you down, but don't flick it up too high either or you'll get thrown off balance. Just make sure you get enough speed on the entry, hold the position for as long as you can and don't be afraid to fall trying. If you're still having trouble, maybe try switching your arm position? Some coaches like you to do it with one arm in front and some like you to have them both stretched back. If one isn't working for you, try the other.
Sit: Again, it's all about the momentum (and, in this case, the balance). There's no distinct rule as to how far you have to sit - you should try to sit as low as possible to begin with, but I think the general rule is that your butt shouldn't sink below the central point (your knee level). You'll know when you're sitting low enough. If sit too far down, you'll start spinning on the heel and you won't be able to hold the position for as long. Make sure you turn your foot out, keep your legs close together, sit straight and hold your arms out in front of you, in line with your free leg. On the entry, go into it with a lot of speed and do one rotation in an open position, then swing your leg straight down into the position. The faster you get into that position, the easier it is to spin.
Loop: The main thing I can tell you is this - don't be scared to fall. You're hardly likely to fall doing a loop anyway, but if you're scared, you have no chance of landing it. As soon as you leave the ice, just say "I'm not putting this foot down", and, even if you feel like you're going to fall, just keep it up off the ice. It sounds difficult but I swear it's the easiest way to start landing jumps. If you're having trouble getting the full rotation (even if it's only by a little bit, this can still be why you're not able to land on one foot), then you need to work on the jump. Make sure you bend your knee before you take off and keep your weight on that one leg. Keep your arms rounded a little and make sure your back arm isn't too far behind you. Then, when you take off, make sure you lift your free nice and high off the ice and swing your arms around really quickly, pulling them in nice and tight. As long as you jump high enough, hold the position and tell yourself not to put that leg down, you should be fine.
Hope that helped :)