Some general tips/things you should know:
1. When you spend a certain amount of bells in the nookling shop and the able sisters (clothing shop) they'll upgrade :3 this is how you unlock shampoodle, the hair salon where you can change your hair and eye color, or wear "makeup" which is actually just a Mii face.
2. You have to completely pay off your first home loan to unlock the island, where you can catch beetles that sell for lots of bells. This is one of the easiest ways to make money in new leaf :3 You can make up to 2 million bells in one trip.
3. Talk to the villagers you want to keep in your town at least twice a day. Ignore the ones you don't want unless they ping you (they look like they're making a surprised face), which means they might tell you they're moving.
4. If you don't have the Beautiful Town ordinance (which you talk to Isabelle to get), you have to water your flowers every day, or they'll die. Other town ordinances include the Bell Boom ordinance (everything sells for more bells), the Night Owl ordinance (all the stores stay open later, including Retail), and the Early Bird ordinance (Stores open earlier).
5. Some public works projects (like the cafe, campsite, reset center, windmill, etc.) are permanent, so you want to be careful where you place them.
6. Your native fruit sells for less in your town than it will in a town with a different native fruit. So try taking your fruit (especially your perfect fruit which sells for 6 times more) to a town with a different native fruit. And if that town happens to be a Bell Boom town, that's even better.
7. Every day, something will sell for extra at Retail. This something will be listed on the board outside Retail. The more streetpasses you get in a day, the more things will sell for extra that day.
8. When you save a lot of bells in the post office, you'll accrue interest over time. You can get up to 99,999 bells in interest each month.
9. Having complete furniture sets in your house gets you more HHA points. When you get the gold badge for the HHA, you get a cool little gold house model lamp

10. Once a week or so, Katrina the fortune teller will appear in your town. Get your fortune read by her 20 times, and she'll open a shop in your town.
That's all the advice I have for now :3 I'll add you, and feel free to visit my town! My fc's in the sidebar.