It is based on the sound at the end of the verb. /t/ and /d/ = "id" started ("start-id") ended ("end-id") /f/, /k/, /p/, /ch/, /th/, /sh/, /ss/ = "t" laughed ("lafft") worked ("workt") clapped ("clappt") watch ("watcht") practiced ("practict") etc. vowel sounds (a, e, i, o, u, etc.) = "d" played ("playd") studied ("studyd") etc.

The past tense of the "regular" verbs end in "ed". The "ed" sounds like "t" or "d" or "id" Here are two videos: http://www.youtube.com/watch?v=R5eIBnKz0tg http://www.youtube.com/watch?v=2s04RenBFEU

If the word ends in anything other than a "t" or "d", simply end it with the "d" sound - "played" - sounds like "playd", "planned" - sounds like "plannd". If the word ends in "t" or "d" include the short "e" sound - "planted" - "plan - ted", "faded" - "fay-ded". [Detailed explanation begins here - ignore if you are bored] This is because any word that ends in "d" would sound the same if the "ed" was not a separate syllable. "T" uses the same rule because "t" and "d" use the tongue in the same way - one is voiced "d" and the other ("t") is not. Trying to end a word with "ted" just saying one consonant would be impossible.

This "-ed" sound is pronounced the way one would say the "Ed" in the name Eddie. When putting a present verb, like "I love" into the past tense you simply add a "-d" to the ends, for the verb ends in the vowel "e" already. For a verb that ends in a consonant, like "I play", you add an "-ed" to the end, to make it "I played". Hope this helped!