the essence of trials riding
Trials riding is all about climbing on any kind of obstacles like a mighty goat. Climbing is one of these moves where you are more likely to smash the bike than yourself (especially the crank set). Walls and concrete kerbs are rather unforgiving for the chainrings (try to practice on wood logs or heavy duty pallets). Start easy and build it up.

7 techniques for all kinds of situations

Using the bunny hop approach at any speed (raw street style). Rolling over the obstacle, a smooth quiet move. In one hop sideways, to bring both wheels on the same level. With a pedal hop, using the combined rollover and pedal hop techniques (for low obstacles). From a static balanced position with the front wheel already onto the obstacle (for accurate positioning in time trials). Banging the front wheel on the upper edge of the obstacle (for higher stuff where rolling over or the bunny hop are not possible) Hooking the edge of the obstacle with your crank (or bash plate), by landing a slow bunny hop or a pedal hop (that way you climb in two steps, but you need a good crank protection).

What pressure for the tyres? It depends on the ground and the sharpness of the edges you climb on. The sharper the edge, the more inflated you want the tyres so that you don't get a double pinch flat when banging the back wheel on it (the unfamous snake bite, rim rails pinching the tube against an edge). For round blunt obstacles like wood logs, less pressure gives extra gripping because the tyre can litteraly grab the edges and shapes. less pressure also gives extra bouncing for landing, and is more comfortable. Fat tyres (2.5" or wider) are the best, and allow a lower pression than thin tyres, so more comfort and more grip.