Common verbs followed directly by an infinitive
In English, when you link two verbs together, you usually insert the word "to" between them. You say "I want to go" or "We hope to see you". Because of this, English speakers learning Portuguese often try to translate that "to" by adding a preposition like a or de before the second verb.
However, many common Portuguese verbs connect directly to a bare infinitive. A bare infinitive is just the dictionary form of the verb, ending in -ar, -er, or -ir. Verbs expressing ability, obligation, intention, and habit usually follow this direct pattern, meaning you can drop the linking word completely.
Verbs like querer, poder, conseguir, and dever never take a preposition before the next verb. They express core concepts like wanting, being able to, managing, and having to do something.
When you want to say you know how to do something, you can use saber directly with an infinitive. You can also say saber como followed by the infinitive, which is equally valid. Both forms are common and correct.
When you talk about things you plan to do, hope to do, or usually do, you also use a direct infinitive. This includes the helper verb ir for the near future, as well as costumar for habits. Words for intending and planning, such as pretender, tencionar, planejar, and planear, follow the same rule. The same goes for decidir and esperar.
Verbs that involve making an attempt or having a strong preference also link directly. You will see this with tentar, procurar, ousar, desejar, and preferir.
The verb precisar is a special case with a regional split. English speakers use "need to", and in Brazilian Portuguese, it is standard to use precisar directly with an infinitive. However, in European Portuguese, the standard rule requires the preposition de, making it precisar de before the infinitive.
If a verb expresses ability, obligation, desire, habit, or a future plan, it likely connects directly to the following infinitive. Resist the urge to translate the English "to" and simply place the bare dictionary form of the second verb right after the first.