Just like you've been told, diesel. I put mine in a garden pressure can so I can spray it a distance and/or "walk" the flame to where I might want it. I use a propane torch (the kind to solder copper pipes with) to start it.
I also prefer to light up just before a storm or just after a storm. This way I get a pass (usually) on having to call my local fire department.
I never never never had ANY idea how fast a fire could move/grow until I started one, one windy day (with permits..).
Long story short, I had a pit & was just going to burn the leaves/growth in the pit to "bring out" the large boulders that I was then going to use for my wall.
Started fire and within 30 seconds I was trying to put it out with the silly rake I'd brought. (oh, and I'd raked around the pit too)
Within probably 2 minutes, I was racing off to get phone & call fire department. It was UNREAL how fast it grew.
So be very careful and if you can use mother nature as your alley, you too, might be able to escape the fun of having about 20 fire fighting vehicles on your property as they were on mine when they came out to bail my HINEY out of a real jam. I think they said about 5 acres burnt up (mostly ground cover).
Now, I will not do fire unless (even if out of permit season) the fire deparment KNOWS what I'm doing, I have cell phone with me at all times, and I prepare burn area and have my backhoe with me. I will also try to wait til just before a rain, during a (mild) rain, or just after a rain.
Don't ever lose sight of safety first.