Quiero = to want something 1) Yo quiero ir a comer (I want to go eat) 2) Yo no quiero hacer mi tarea (I do not want to do my homework) Quisiera = to wish to do something (but most likely not possible) 1) Quisiera poder ir al cine con mis amigos (I wish I could go to the movies with my friends) 2) Como quisiera poder verla una vez mas (How I wish I could see her one more time)

When you say "quiero" you are communicating a decision or something which you are very sure. Ex: Quiero ir al cine. If you say "quisiera", you are expressing a wish that is not likely to be carried out immediately. "Quisiera ir al cine, pero no puedo. Tengo que trabajar."