5: A couple of ways to gain some free stars
Stars (or star coins, koins, or whatever) are the premium currency of the game. If you want to get more of them for free, save them up. You can get them from completing quests, completing achievements, from gaining experience levels, and most importantly, from moving up by one list (from the D-list to the C-list, etc). They will come slowly but they will add up over time.
4: Tap on everything that falls out when you complete an action.
If you just let it disappear, it will still be collected. However, for everything that you tap and collect yourself, you will drop your energy counter by 5 seconds. That means for those actions during assignments which cost 8 energy, by the time you tap on everything, you may end up getting one of your energy points back immediately.
3: Buy new houses, apartments and condos.
While they are by no means a requirement, they are certainly good to have. These will allow you to buy more furniture and decorations, further increasing your star power and your heart power. In addition, you can hold more pets in some dwellings than in others. They are expensive but they can be worth it if you use them right.
2: Get experience without spending any energy by drinking at the bar.
Go to any bar of your choice and order drinks from the bartender. The one in Downtown is a good one because it only costs 10 bucks for a drink. Every time that you order something you will earn experience points, so with enough patience, you can actually get yourself a level up using only cash, rather than spending stars to refill your energy.
1: What to do if you get stuck in a level?
If you get stuck with absolutely no cash, stick around for awhile and tap on the background scenery to get some free cash, then come back and tap it later (it restores every five minutes or so). Or, simply wait it out if you have an assignment that you have recently completed that you are waiting to debut. Once it comes out you will earn a monetary bonus, allowing you to hit the bus or plane again.