job levels

what exactly is the criteria which increases your job levels?
is it a set number of battles or does it depend on which enemies you fight?
thanks much

It depends on what you do in battle

such as?

Pretty much anything, whether be defending, or attacking, or using job abilities

jus use a job command rather than attack then?

The game keeps an internal count, JobExp, that increases each time to take a valid action in battle, which is basically anything that doesn't involve fleeing or changing row. Depending on what version you're using the amount it goes up each use changes. In the NES version different commands on different classes made it go up by different amounts e.g. the Attack command would increase it by 8. In the DS version each class gains experience at the same rate for each command up until job level 14 (the scholar gains slightly more but due to the amount technically doesn't increase in job level any faster). After this each class gains different amounts of JobExp. For example Freelancers gain 20 points per command, while Onion Knights gain a measly 8 points. Regardless of how JobExp is gained, you will go up in Job Level for every 99 points you gain. Note you can't gain more than one Job Level per battle in either version, and once you do reach 99 JobExp you'll go back down to 0 for the next Job Level i.e. you can't stack up JobExp in one battle to say 990 and get 10 Job Levels. You'll simply gain one Job Level and JobExp will be reset to 0.