Use these videos to review grammar concepts:

*The preterite vs. imperfect video by Señor Jordan has links in the video to other conjugation videos that you may find very helpful.  I didn't have time to pull them out individually, put you'll see the links about 10 seconds into the preterite/imperfect video.
Review & practice your skills. . .
Pretérito v. Imperfecto:  definitions & examples
Prueba de pretérito y el imperfecto