As far as I can think of:

1) When a word ends in a vowel sound, or an 'j', 'b', 'g', 'l', 'm', 'n', 'v' or 'z'  sound, the 'ed' is said like a 'd':

Ex:

Watered is pronounced like water + d.

Shared is pronounced like share + d.

Aged = Age + d (The 'g' in 'age' is pronounced like a 'j')

Sobbed = Sob + d

Rammed = Ram + d

Maned = Mane + d

2) When a word ends in a 't', 'd' or sometimes a 'ch' sound, the 'ed' is said like 'ed'/'id'. The reason I say 'ed'/'id' is because the sound is pronounced so softly and lazily that no one actually bothers to pronounce a specific vowel. I suspect some accents might do this for 'k' sounds as well.

Ex:

Matted = Mat + ed

Abducted = Abduct + ed

3) When a word ends in a 'k', 'f', 'p', 's', 'th', 'sh' or 'ch' sound,  the 'ed' is pronounced like a 't'.

Ex:

Washed = Wash + t

Sacked = Sack + t

Flapped = Flap + t

I've based this on all the examples I can think of off the top of my head. If I missed anything, or if anyone disagrees, please let me know.

Good luck.  This is a hard thing to learn without hearing examples over and over.  The difference between ending with "t" and "d" is subtle and if you say it wrong you will still be understood.  The t has a harder sound and the d softer, but they are similar especially at the end of a word.  At the beginning of a word the difference is more noticeable, for example, tea and door.  If you pronouce door as toor, you will be misunderstood, but if you pronounce talked as with a soft d, you will be understood.

Hamid:

If I understand your question, you want to know whether you pronounce the "ed" as a T or a D.

Am I right?

Here is a trick that seems to work:

1. Before you add the -ed, say the word several times  to yourself out loud.

a. When you say "talk," does your tongue go up or down in your mouth? I think that it rises. Right? Well, if it rises, then "talkED" is pronounced like "talk" + "T." Something like "talkTUH."

b When you say "play," does your tongue go up or down in your mouth? I think that it goes down. Right? Well, if it goes down, then "playED" is pronounced like "play" + "D." Something like "playDUH."

in short:

- /t/ when the word end: ss, sh, ch, gh, p/ pe, k/ke, f

eg: thanked, accused, reported,...

- /id/: when the word end: t/ te or d/ de

eg: admtted, suggested, insitted,...

- /d/: the rest

eg: warned, denied, happned,...

Wish this will help U!!!

For regular verbs these 2 rules apply: If the verb is ending with an E you just add the D. If the verb ends with a Y you take away the Y and change it to IED. If the verb is irregular you just have to memorize the past tense of the verb. Below is a list of examples that may help you understand.

Verbs ending with E:

Dance - Danced

Hike - Hiked

Bike - biked (when using it as a verb)

Verbs ending in Y:

Try - Tried

Cry - Cried

Study - Studied

Irregular Past tense verbs:

Become - became

leave - left

make - made