Thinking back to when I learned...I practiced by jumping a leave rake laid in the driveway. I started by doing both wheels at once then moved on to the front wheel first stuff later. Once you find the motion you'll be able to jump much higher pretty quickly. Don't be surprised if you can clear a foot in only a few weeks.

A funny memory - I took my buddy's 7-inch travel MTB for a spin one day. I headed for the curb with some speed and barely, by the slimmest of margins, made it up. For a moment I thought that I was going to face plant into the concrete. Apparently a 45 lb bike with a big squishy suspension isn't as agile as a BMX bike. Who would have thunk?