I would agree with most of what's been said already. I still have a bit of anxiety every time.
I like to have quiet music playing, ambient or soothing tracks like this are usually my favorites
http://www.youtube.com/watch?v=JBDbx28PXGA DMT by Shpongle is another good one if you're more adventurous.
Definitely be in a comfortable place where you won't be bothered.
If you're uncomfortable for any reason (drunk, upset stomach, headache etc.) save it for later.
I too am a bit put off by the physical discomfort of the spice, but for me the overall experience is worth it. I've found that keeping my eyes closed through the duration of the trip helps keep my focus off of the physical world.
One thing that surprised me was how much more uncomfortable I felt on smaller amounts 20-30mg than with my average 50-60mg dose. I could smoke 10mg and get a fun head-change or a full breakthrough dose and have a great experience, but for some reason the mid-level doses leave me with an uncomfortable body high and a longing for something more.
These are just my personal experiences, I hope they might help you, but please don't do anything you don't feel comfortable with.