Well I've kind of got this idea from ZB Advanced Money Code made by Viral. You get different amount of money per topic & post. And it's a range which the script randomly selects what amount you get. So for example:
Minimum per topic: 6
Max per topic: 12
Minimum per post: 3
Max per post: 5

That why your credits wouldn't go up as quick and people would have to post more. So it helps BB become even more active.

Something like, you get more credits for the more effort you put into making a topic/post. And less for having not much words in your post?

It could work like that. But I was getting at - the script randomly chooses the amount you get within those ranges or what ever Cory uses for the min & max.

Ah I see, you'll have to ask Mike (Mwr247) if the code runs like that, as he was the one who made it.

Unfortunately, I've substituted efficiency for functionality in the workings of this code, which limits it somewhat. To prevent glitching and keeping it as simple as possible, credits are accounted for by taking your post count and then offsetting it by the number in a file, which are changed by credit transfers. I am considering revising the code in a way that's both efficient and flexible, so I'll consider modifying it to your recommendations once I get started on that.

The things mentioned wopuld be cool..

I don't really understand how credits are obtained or how o see how many I have - is there maybe a post I can be directed to that explains this ?

The credit system is explained Here :)
And telling you that just earned me five more credits ;) :P

Ah thanks, I've worked out why I wasn't seeing it now - noscript was blocking it ^^