A regular verb conjugates into the past tense and past participle by simply adding -ed to the end of the infinitive: ask/asked, talk/talked, watch/watched etc. Irregular verbs, on the other hand, each follow their own set of rules of conjugation. There are, however, some basic patterns that can help you remember how to conjugate some of these irregular verbs.
Many verbs ending in -ow are made past tense changing the -ow to -ew, and past participle by adding an -n the -ow, such as grow/grew/grown, know/knew/known, and throw/threw/thrown. Here is the verb "to know" in the past and past participle:
Don't think you knew you were in my song.
Caption 31, David Bowie: Five Years
David Jones, now little better known as David Bowie.
Caption 1, David Bowie: Interview at 17!
Here too you have to be careful though, as some verbs ending in -ow are regular, such as tow/towed/towed and flow/flowed/flowed, and some irregular ones ending in -ew in the past tense and -own in the past participle don't end in -ow in the infinitive form, such as fly/flew/flown.
Another pattern can be seen in irregular which end in -ght in the past and past participle, such as buy/bought/bought, teach/taught/taught, and think/thought/thought. Here is the verb "to think" in the present and past tense:
Well, I think we're all fairly tolerant.
Caption 16, David Bowie: Interview at 17!
I never thought I'd need so many people.
Caption 19, David Bowie: Five Years