Caltrops might help you out.
Depends on the terrain in question. For instance, you could cause an avalanche or a rockslide, or release the dam or knock over a tree.
You could set fire to dry grass. Kick some floorboards loose. Smash some tiles with your hammer.
The simplest thing would be to look around for a gravely patch or similar, and get yourself behind it before the other guy can act or get to you.
Most things that would take only a standard or full round would be things that already exist in the terrain that you are just helping along (such as kicking loose some rocks to start a slide). Others will take longer. Ultimately, there are precious few ways to change terrain without magic that do not involve detailed description from, and cooperation on the part of the GM, or some preparation.
Caltrops, as mentioned, is one of them. But again... you must be prepared.
Barbarian rage power: Ground Breaker
Carry around a chair every. Where you.go when fight starts break it on floor
Flask of grease or oil, (acts as grease spell for one square), caltrops, using objects around (table, chairs). Marbles. Smashing the wooden floor (if available, and deepenough to make difficult terrain...my dog (no seriously, she is always underfoot).