"Full" log file to large and i need to split it every 12 hours?

Hi, I have my “Full” log file that is too large by the end of day so i need to split it every 12 hours so they are manageable to parse. I think i would need to change something in the log rotate utility but i dont know if i would change the rotation from daily to hourly or just change the size??

man logrotate

(http://linux.die.net/man/8/logrotate)