How do you form the past and past participle of verbs?

Answer 1

For regular verbs that do not end in 'e', or a consonant followed by a 'y', you add 'ed' to form both the past and the past participle:

To jump, I jumped, I have jumped.
To fetch, I fetched, I have fetched.
To defend, I defended, I have defended.

For regular verbs that end in 'e', you add 'd' to form both the past and the past participle:

To hope, I hoped, I have hoped.
To promise, I promised, I have promised.
To devise, I devised, I have devised.

For regular verbs that end in a consonant followed by a 'y', you change the 'y' into 'i' and add 'ed' to form both the past and the past participle:

To sally, I sallied, I have sallied.

To bloody, I bloodied, I have bloodied.

For irregular verbs, you must learn each one individually. There are some patterns that may help you, but you must always beware of exceptions (English has a lot of those).

Here is one example of a pattern. Many monosyllabic verbs with an 'i' in the infinitive form the past and the past participle by changing the vowel to an 'a' and a 'u' respectively:

To sing, I sang, I have sung.
To drink, I drank, I have drunk.
To swim, I swam, I have swum.

But:
To swing, I swung (rarely 'I swang'), I have swung.