One of the biggest advantages to learning English is the fact that, in English, you have a maximum of FIVE words to express any verb idea:
º the infinitive - TO BE ... TO EAT....TO PAINT
º the present simple - AM/ARE/IS....EAT(S)...PAINT(S)
º the past simple - WAS/WERE...ATE...PAINTED
º the present participle - BEING...EATING...PAINTING... and...
º the past participle - BEEN...EATEN...PAINTED
For people who are learning English, this is either a blessing or a curse. It's a blessing (what's the third person past preterit subjunctive of TO PAINT? Who cares!!), but it can cause difficulties for Spanish speakers of English for two reasons.
The first is obvious: If you're used to using a whole bunch of different words to express very specific ideas, it may feel strange, at first, to limit yourself to only a couple of words.
The second reason is the most difficult and it's the kind of problem that causes people to fail oral exams - it's EXACTLY the kind of mistake the examiner listens for, to check if you're translating or you're really using English.
Let's take idea as an example.
Imagine that you're at a party, and a drunk, obnoxious person comes up to you and starts bugging you. You ask him nicely to leave you alone, but he won't go. Then he tries to hit you! You go to the host of the party, and, in Spanish, you say....
¡QUIERO QUE SE VAYA!
This is a perfect example of when you use subjunctive in Spanish:
a) the two verbs have different subjects: (yo) quiero // (él) se vaya.
b) you can't control the result: quiero doesn't guarantee that the second action (irse) is going to happen.
But in English, you cannot say: *I want that he leaves.
Look at the first verb: want. In English, WANT is always transitive: you always want something, or you want someone to do another action. Since you're the speaker and your want is the most important verb in the sentence, you have to complete that verb first.
I want (direct object)...
The direct object of want in this case is HIM, because a verb cannot be a direct object.
I want him (third person singular object pronoun)
So what happens with the second verb? Ah. Since HIM is already the direct object of WANT, it can't ALSO be the subject of LEAVE. It can't do both jobs. As a result, WANT doesn't have a subject, which means it must be infinitive:
I want him to leave.
This is correct English: Two verbs, but only ONE possible subject, so the second verb has to be put into the infinitive. Spanish looks at this situation and sees a philosophical problem; English looks at the situation and sees structural problems with the verbs.
It's worth remembering tthis is the kind of mistake that examiners listen for, especially in First Certificate speaking exams. Remember, it's called the First because it's the first Cambridge exam where you must show that you can communicate without translating. And it's especially important to use common verbs like WANT, HOPE, LIKE properly.
If you're not sure how to organize the information after the verb, a quality English-only dictionary like the Oxford University Press series of dictionaries will describe what verb patterns to use, depending on how you use the verb. (In the Oxford dictionaries, verbs that need infinitives after have the V+[TO- inf] code after them.)