Like in all languages, in Spanish, expressing a request can be done in different ways — more politely or more commandingly. In Spanish, for example, we can ask for a glass of water in the following ways:
1. ¡Un vaso de agua! – A glass of water!
2. ¡Tráeme un vaso de agua, anda! – Bring me a glass of water, come on!
3. ¡Que me traigas un vaso de agua! – Bring me a glass of water!
4. ¡Tráigame un vaso de agua, por favor! – Bring me a glass of water, please!
5. ¿Me puedes traer un vaso de agua? – Can you bring me a glass of water?
6. ¿Te importa traerme un vaso de agua? – Would you mind bringing me a glass of water?
In a similar way we can use:
pasar la sal – pass the salt
pasar el cuchillo – pass the knife
traer pan – bring bread and so on.
Which of these ways of expressing yourself you choose depends on you, but I hope you are aware... that in order not to be answered 'Bring the water yourself!' it is good to use the more polite options – 4, 5, and 6.