Alien Crash Site: Fulfill all of XY-XY's aspirations and make him friends with Jonas. This will unlock The Bio-Dome.
Cliffside Retreat: Fulfill all of Isabella's Wants and make her happy. Note: It may be difficult and take some time to get her to make a sandwich.
HMS Amore: Fulfill all of Betty's Wants until she is Platinum. She will then tell you where the next location is. One of her wants will be to marry Captain Nelson.
Jugen House: Fulfill all of Toothless Joe's aspirations until your Sim gets "Visit New Location" as one of their aspirations. Then, go back to Tranquillity Falls and your aspiration will change to "Help Chantal". To do this, just keep fulfilling her wants until she is Platinum (a job in Art). This will unlock the Alien Crash Site.
Orbit Room: Become friends with Red S, then serve him some food. Then, move back to Sunset Canyon and make Red S and Helga fall in love and get married. Red S will now live there, and you can control him. Do whatever is needed to get Red S in a Platinum mood. He will tell you how to get to Tranquillity Falls.
Rockwall Acres: Follow the instructions given to unlock this area.
Shoreline Trails: Buy a Foosball Table. When a Want that is described as "Beat Torin at Foosball" appears, wait for Torin to play, then click the "Challenge" option and defeat him.
Sunset Canyon: Bring Helga, Billy, and Sheila back to life, build a kitchen, clean up the mess, build a bathroom, and give them beds to sleep in. They will then tell you the next location.
Tranquillity Falls: Fulfill all of Larry and Chantal's wants to put them in a Platinum mood. After both are in a Platinum mood they will tell you where Jugen House's is located, and it will be unlocked.