To use the conditional tense, what verb endings do I commonly use?

The conditional tense is used to say what would happen if something else were to occur or to talk about intentions to do something. 

If I was was rich, I would buy a big house. 

Si j'etais riche, je acheterais une grande maison.

I would like to talk with a 15 year old young person.

J'aimerais correspondre avec des jeunes de 15 ans.

I would like to go to the cinema

Je voudrais aller au cinema.