The past tense / participle of regular verbs all end in -ed, but irregular verbs have no rules for conjugation. These can only be learnt in context - sorry!
All verbs have a base form (the infinitive). e.g. to run.
A present continuous / gerund (ing) form where ing is added to the end of the verb. e.g. running.
A present simple -s form where s is added to the end of the verb. e.g. runs.
So far so good, but then we come to:-
The past tense form which must be learnt. e.g. ran
The past participle form which must be learnt. e.g. run
Sometimes the infinitive, past tense and past participle forms are different.
Sometimes the past tense and the past participle are the same, but different from the infinitive.
And for some irregular verbs, all three forms are the same.
We have put together a comprehensive list of irregular verbs for the past and past participle forms, along with a pronunciation guide.