Past simple with regular verbs :
For regular verbs add -ed to the infinitive

e.g.
Start      ⇒   Started
Play       ⇒   Played
Watch   ⇒   Watched
Talk       ⇒   Talked

CAREFUL!
1. If a verb ends in -e, you just add d
e.g.
Liked   ⇒   Liked
Agree   ⇒   Agreed

2. If a verb ends in a vowel and a consonant, the consonant is usually doubled
e.g.
Plan   ⇒   Planned
Pop    ⇒   Popped

3. If a verbs ends in consonant + y, you take off the y and add -ied
e.g.
Carry  ⇒  Carried

4. If the word ends in a vowel + y, you add -ed
e.g.
Enjoy  ⇒  Enjoyed