Subjonctif

For emotions and things that are possible but not certain, expresses doubt - douter, il semble, il est peu probable - Utilise au negatif aussi

Conditionnel

For phrases with "would" - se douter, il me semble, il est probable

For facts and questions, expresses certainty - Il est certain qu’il va pleuvoir demain

For actions that occured prior to other past actions - eg I had washed = j'avais lave

For actions that WILL HAVE happened in the future (have not yet happened) - eg I will have washed = j'aurai lave