I saw him, that is to say I've seen him.

Regular VERBS are easy, just add ~ed to the end.

(e.g Jumped, kicked, cooked etc)

But IRREGULAR VERBS are difficult.

Here is a good list of irregular verbs.

http://www2.gsu.edu/~wwwesl/egw/verbs.htm

Try and remember as many as you can.
Good luck, there are SO many!