To form a conditional clause you need to start with the word 'si' - if, then make sure that you are using the right tenses for the rest of the sentence!
1. Si + present + future (e.g. si je vais, il ira aussi - if I go, he will go too).
2. Si + imperfect + conditional (e.g. si j'allais, il irait aussi - if I went, he would go too).
3. Si + pluperfect + conditional perfect (e.g. si j'étais allée, il serait allé aussi - if I had gone, he would have gone too).
These look very impressive in a written exam as they are quite complex, using a variety of tenses so try to slip one or two into an essay if you can to gain extra marks!