As with any tone a lot depends on personal taste. Having said that I can give you some common ideas that people use to get slap bass sounds.
The EQ whether from your bass, amp or both is most commonly more lows and highs while scooping the mids. On a graphic EQ this would look like a smile. You need to do this to taste and be careful not to overdue it. Your mids hold a lot of the "definition" in your tone so if it's cut too much you loose clarity. By turning the mids down you get that punchy slap tone that moves air.
My advice is too find a tone you like on a CD and try and reproduce it. This is done in the studio a lot when a specific tone is wanted.
Also new strings will give you a more snappy, punchy tone.
Lastly I tend to use my front pickup or a blend of both rather than my bridge pickup I have a bass with 2 pickups.
Hope this helps.
Best