"Que vs a" after verbs

"Que vs a" after verbs
 

I have to...
I need to...

To substitute "to", sometimes "que" is used and sometimes "a". Is there some sort of rule? Or is it determined by the verb?

To have to is tener que. Tiene que recordarlo. It's easy use and very useful

To need to necesitar+ infinitive is a similar usage, but it doesn't use que.

Poli is right. I will just add that the preposition needed is determined by the verb. The use of prepositions is one of the most difficult things when learning a foreign language, but with practice one ends up developing an intuition for the verb structures.

Thanks
 

That helps a lot, thanks. I would mention though that after "necesitar", "que" is actually used... At least from my experience

Oh, yes, but then it is translated as "to need that", rather than "to need to". ;)

- Necesito comprar pan. (necesitar + infinitive)
I need to buy bread.
- Necesito que Juan compre pan. (necesitar + que + subjunctive)
I need that Juan buys bread.

- Necesitas comer más verduras. (necesitar + infinitive)
You need to eat more vegetables.
- Necesitas que tu comida tenga más verduras. (necesitar + que + subjunctive)
You need that your food has more vegetables.


By the way, you might find this thread useful. :)