[Rusty]

The conditional would be used anytime you use the conditional in English. The subjunctive is almost dead in English, so I can't say the same thing.

The subjunctive is very important to master.
There are many rules that govern the subjunctive mood. You asked the same question almost one year ago!

Let me see if I can find other threads that'll help.
http://forums.tomisimo.org/showthread.php?t=2409
http://forums.tomisimo.org/showthread.php?t=4964
http://forums.tomisimo.org/showthread.php?t=2424

There are many others, and there are many sites that can help you pin down some of the rules.
http://www.lingolex.com/swom/wom-subj.htm
http://www.studyspanish.com/lessons/subj1.htm
http://www.studyspanish.com/lessons/subj2.htm
http://www.studyspanish.com/lessons/subj3.htm
http://www.studyspanish.com/lessons/subj4.htm
http://www.studyspanish.com/lessons/subj5.htm
http://www.studyspanish.com/lessons/subj6.htm
http://www.studyspanish.com/lessons/subj7.htm
http://www.studyspanish.com/lessons/subj8.htm