Have you taken a look on Trashzen at some techniques for getting up stuff? Some good guides on there that would probably come in handy and they have video examples as well. Purely assuming you ride a mod I'd suggest trying to bunnyhop up them straight to rear, I find it a lot easier on both my bikes but especially my mod than half pedalling.
One tip I can suggest is to lean back as you bring the front wheel up so you can spring yourself forward as you kick, go at a nice steady pace and make sure your not trying from too far away. Also one last thing which could just be me but try going up them from different sides, I often find that if I can't get up a wall or a ledge if I try doing it a few feet further down the wall it makes all the difference as you'll find yourself trying to launch up from the exact same spot all the time and if it's too far away you'll never make it up. If you keep changing position your never trying to mimic what you just did.