MX vs. ATV Reflex

Get on the crappiest MX Lite you have, you don't want too much speed here. I used the default Blaze 250.

Go somewhere with a lot of space that's flat. Reyes AZ is a good one. Once you're aimed at the wide open space, hit Y to set your marker so you can just jump back to it with B *when* you screw up.

Set the user camera to a side-on view, a bit like in Trials HD.

Accelerate, and once you've moving, pull back on the right stick. Keep holding back on the right stick and on the accelerator, and GENTLY tap the brake to stop yourself tilting back too far. Only the slightest touch otherwise you'll plant the front wheel back down.

It might take a few attempts.

Go somewhere with lots of flat space. Reyes AZ is a good place. (Just like Suicide Perkies said). You aren't really required to have a slow bike here. You can try different types of bikes like the fast and slow ones I mentioned to see which one works for you. When you begin, go forward, and turn a tiny bit to the left from the spawn point. Keep going until you hit some very dry sand. This is a good starting point. If you turn back around, you'll see a trail leading up a hill. Set a checkpoint where you are and ride to this point when you do the wheelie. You'll have plenty of flat space. For the wheelie, you need to find the perfect balancing point. Tapping the brake is okay, if you're comfortable with it, but if you do it too much, it ends the wheelie. You can experiment with methods from different guides to see what works the best for you and your bike. One thing you can try is to change the angle of the user camera so that you're looking at yourself from the side. Credit goes to Suicide Perkies for this method. This will make it look like you're playing Trials HD. This can make the wheelie much easier for you since you can see your exact angle. I found that when my rider leaned back far enough, there was a point where his angle stayed steady much more easily. This is the critical point of balance you're looking for. It takes a few tries to get a feel for it. This critical point will only last for a small amount of time. However, 150 ft. isn't that long. It's just twice the stoppie distance required to get the Stoppie Master achievement. With a reasonable bike, your wheelie's length may easily exceed 150 ft. After a few tries, you'll get it. It depends on a variety of factors.