Setting up ip tables

I have looked at several sources for info on how to set up iptables. I have checked that ip tables is enabled and it is However i compiled a script to set the rules (as its kinda pointless withoout them :)) Neways when i ran the script iptables came back with an error saying it did not recognise INPUT So i thought i must have something wrong and i double checked in a book i have (Linux bible) and online and syntax was as far as i could tell correct so i removed the lines in the script to do with INPUT to see if i had the same problems with OUTPUT and yes i did. My next thought was maby it was the script so i tried giving the commands manually and the same happened. Any ideas?
Thx

If you could post the exact commands you used that would help.

Maybe even the results from 'iptables -L' just so we can see how everythings structured. You can't delete INPUT or OUTPUT, so there's something else going on.