Verbs followed directly by an infinitive
English relies heavily on the word "to" to connect actions together. If you want to express a desire, obligation, or preference, you naturally say things like "I want to sleep" or "I plan to eat". English speakers learning Italian often try to translate this literally by inserting the prepositions a or di between two verbs.
However, in Italian, a special group of very common verbs skips this connecting word entirely. You just place the main conjugated verb directly next to an infinitive verb (a verb in its dictionary form, ending in -are, -ere, or -ire). The "to" is already built into the Italian infinitive, so no extra preposition is needed.
The most frequent verbs that use this direct connection are the modal verbs. These are core verbs like volere, potere, and dovere. When you use them to describe another action, the second verb stays in the infinitive. The verb sapere also works this way when you use it to mean knowing how to do something.
When you talk about activities you enjoy or hate, the connecting preposition is also dropped. Verbs of preference like amare, adorare, odiare, and detestare attach directly to the next action. The verb preferire follows the exact same pattern, as does sopportare when you cannot bear doing something.
A few other useful verbs express intentions or wishes and are also followed by an infinitive. You will often see this direct connection with desiderare, intendere, and osare.
When using modal verbs, preference verbs, or verbs of intention, the English word "to" is already covered by the Italian infinitive ending. Resist the temptation to insert a or di, and simply link your conjugated verb directly to the infinitive action.