There are quite a few ways you could do this. One is by having your characters abuse the Golem's rolling strategy, as mentioned above, but there are others. For instance, their Pokédex entry states that Golem are capable of leaping vast distances very quickly by using a series of minor Explosions to propel themselves. I don't know where you're setting the battle, but several locations would offer the option of tricking it this way in a similar manner to the Rollout abuse. It's not a huge difference, but unlike the rolling trick, it's not actually been done before (to my knowledge, at least).
Alternatively, you could start to think about how a Golem would fight. They're huge, unstoppably strong and terminally slow; they probably either try to back their enemies into a corner so they can't dodge their attacks, close the distance between them as swiftly as possible by rolling or Explosion-jumping and then punch, slam and bite them into submission. Avoiding this would be key to the battle, since if you can avoid being trapped the Golem would have to rely on its limited ranged movepool, mainly Earthquake and Rock Slide/Stone Edge, at least two of which are relatively easy to dodge.
That's how not to be beaten, then, but how to win? Well, Golem have a tiny head in relation to their body size; I think it's fair to say they're not going to be the smartest of enemies. If this is a Trainer battle, you could try preventing it from hearing its master's orders (perhaps deafening it with SonicBoom, Astonish or Uproar, or by caking mud around its ears with Mud Slap or something - since Golem are obviously reptilian, chances are that their hearing isn't too hot). In a situation like that, it might well panic and start lashing out wildly, perhaps not even using moves; if you get to that stage, as long as you can remain out of its reach, it's probably going to tire itself out eventually. Even if it doesn't panic, it's not going to be able to see through any tricks you might try to pull on it in the same way its Trainer would be able to, so you could lure it in close, status it and wait for it to either faint from poison or knock itself out from confusion. Alternatively (and this depends on the location) it could blunder into something it shouldn't, perhaps Earthquaking something that collapses onto it - again, something it wouldn't have done if it had had its Trainer to command it.
What if it's a wild one? Well, it really all depends on the setting here. You could lure it over a bridge where its weight will make it fall through into a river below - or, make it use Earthquake or Stone Edge on a bridge, destroying it and making it fall. I'm pretty sure Golem are too heavy to swim, and by the time it gets out of the river your characters could easily make their mistake. If no bridge is available, a frozen lake might be a good substitute.
The key is to be creative. Think about the environment, and think about how each Pokémon move actually works. Even Splash has a use; it might do nothing in terms of harming an opponent, but I bet the randomly-flying water droplets would scramble a Zubat's sonar and let something approach it through the veil of water. Actually, speaking of that, Golem seem to me like they would have comparatively weak eyesight, so a similar tactic might confuse them.
Well, I've rambled for long enough, and I don't think I've actually said anything that anyone else didn't say. Sorry about that. I guess the main point is that for an answer more interesting than a standard status defeat, use the environment against the enemy and your Pokémon's moves creatively.