Правило очень простое: told употребляется в том случае, когда что-то говорится кому-либо (Он сказал мне, что тест был трудный), said когда просто есть констатация факта (Он сказал, что тест был трудным).
1.She said everything.
2.She told them everything.
3.Who told you this?
4.Who said it's cold today?
5.He said that the trip was interesting.
6.And then he said something funny.
7.The teacher told us to come early.
8.The teacher said that the text was difficult.
9.The teacher told to us that the text was difficult.
10."He'llcome at 7o'clock,"she said guickly.