When using commands to make requests, tone is important as they can sound rude or abrupt. In order to avoid this, there are other ways to make requests, usually in the form of a question.
You can simply use the present indicative tense:
¿Abres la ventana por favor?
Can you open the window, please?
Or use a modal verb like poder(to be able to):
¿Puedes abrir la ventana?
Can you open the window?
To be extra polite you can use the conditional simple tense:
¿Podrías abrir la ventana por favor?
Could you open the window, please?