The circumstances in the dream are very important.
If you see the Devil in his usual context – in a pit full of fire, surrounded by demons – then you’d better ask yourself what guilty secret you’re hiding and how it applies to your present circumstances.
If the Devil speaks to you and seems friendly, then you’re going to be faced with a temptation that will prove difficult to resist.
If you fight him, you’ll resist that temptation.
If you see the Devil with someone you know, that person may be trying to manipulate you to serve his own ends.