You should check that your code fails gracefully, too. That was a really hard one for me to learn- I wrote code that had all kinds of silly dependecies (servers being kept up by other people's personal cron jobs, report files being available in random places, etc), and then forgot about the scripts. When the script would start randomly failing because something it had depended on changed, it would take me forever to track down the problem. I try to be really paranoid now, and wrap stuff in evals, check return codes from system calls, & write error strings that make sense. It's good to not have to explain to people that you have no clue why your tool started failing over weekend & that you'll have to get back to them in a day or two. Although I guess that if you're leaving, you won't have to deal with that part. (:
It's really hard to make the adjustment from hacking code for your CS homework or your own website to writing code that people depend on to do work, though. I'm always finding new things that I should be doing & becoming embarassed that I hadn't been doing them before. -- cat