Originally posted by Gladi8er65:

If you don't want to cheat by using the map website, the 'best' way to find the trader is to sail (use one of the boats NOT the raft), sail along the shore of the islands and eventually you should see a 'money bag' icon appear on your map, which is the trader.

There are like 8 or 9 possible locations on each world where the trader might spawn, and once, you see the money bag icon, he will only spawn at that location, on that map.

He is not always going to be on the main starting island, search other islands.

Also to add to this. The trader is always in the Black Forest.