How do you say standing by in spanish?

There is no direct translation to the English phrase "stand by" meaning to be waiting for instruction or just to wait. Basically the phrase translates as "Wait" or "Waiting for your instructions"

Esperando sus instrucciones.

The Words "standing by" meaning literally to stand by an objcet like "standing by the mailbox" would be "de pie al lado de" On foot next to...