If you're coming from Mercury, then you should set your trajectory away from the sun. Earth is right after Venus, so, if you see Mars, then you have gone too far.

Conversely, snowbirds should put on their sunglasses and head towards the giant nuclear reactor. Earth is the third planet from such a reactor.

Real time traffic report: If you're coming from another star system, then you may experience interference when traveling through the Kuiper Belt.