Certain Mission agents will locate people for you (for a fee of course). The locator agent has a time limit before their services can be used again, and they can only locate people in a certain distance depending on the agents level.
Low-level locators are limited in range, but a higher-level agent can locate a player anywhere in EVE. And the delay is much shorter. You get the location within 0-10 minutes (depending on how far away they are), and can use the agent again in 15 minutes to an hour.
After the agent finds the player you will get a eve-mail from him/her telling you where the player is at the moment.