One of my favorite ways to earn credits is visit the NPC (Non playing characters) daily, I also like to play pirates at the lower levels as capture the flag may earn you a lot of credits if your good at it.
Along with the NPC, do the street party music first - the rest next (I often stop to say hello on my way, pick up new items in stores, etc.) and then come back to street party for 25 more credits in 1/2 hour. You can get them every half hour, so if you aren't busy just leave and get them! lol
1. getting ALL NPCs
2. Playing Music Game ( every fifteen minutes to half hour, you don't have to wait an hour )
last but not least..
the major credit getter..
FIREWORKS GAME!!! ( about 7-8 games should do the trick )
WARNING: You must be good at the game.. I get about 1,300 credits per game by..
the 300 credits are from getting to Level 5
the 1000 credits are from getting over 240,000 points but not winning
hope this helps! I discovered a hidden fireworks talent from practicing over and over - trust me, even if you're not good at the game now, it gets better - yes, the game is long, but it pays off!!