verbs that change meaning in preterite

conocer (present): to know; to be acquainted with
conocer (preterite): to meet

saber (present): to know information; to know how to do something
saber (preterite): to find out; to learn

poder (present): to be able; can
poder (preterite): to manage; to succeed (could and did)
no poder (preterite): to fail (to)

querer (present): to want; to love
querer (preterite): to try
no querer (preterite): to refuse (to)