This is a complete lesson to teach 2nd conditional and some alternatives for the use of if. It starts out with a vocabulary exercise which is related to the song Grenade by Bruno Mars. In the song worksheet Ss have to listen to the song and find the extra word in each line. Then is the guided discovery for the 2nd conditional based on the song, which has three discovery exercises and then there is one controlled practice. You could finish it off with a freer exercise using questions for the Ss to write and then ask and answer in pairs.