There are different ways to do a wallride, and different ways to think about how you perform the trick.
There are different ways to do a wallride, and different ways to think about how you perform the trick - just like all the other tricks! My way would be like this:
Approach the wall at about a 45 degree (or even a little less) angle. The faster you are going the longer you will ride. Jump at a fair distance from the wall. If you jump too late you will not be able to get your skates onto the wall in time and you will just end up splatting on you side and looking like an idiot. As you are jumping towards the wall bring your skates up and perpendicular to the wall. Kind of tilt your body away from the wall so that you are also perpendicular. Then gently set you wheels onto the surface and ride until you lose momentum and fall off.
Timing the jump is the key thing. It's not really a hard thing to do but it just takes practice. You might want to practice it first without your skates on. Just run upto the wall, jump, and then push back off.
After a little bit of practice you can try different variations. You could approach the wall from the other direction and doing a 270 off the wall. Land with one foot - grab the other. Transfer to another obstacle. Go try it!