1. Buy all the items from your stores. Later on you'll get a store upgrade in which you can re-order most stuff you've had in your inventory.
2. Buy all the stuff from your Nooks because it only upgrades after you spend a certain amount of money.
3. Going to Tortimer Island, as soon as you get that, fishing/catching bugs there and selling them in your town is the best way to get a good amount of money before you find alternative/personal ways to make even more.
4. Your native fruit has a perfect version to it. When you plant perfect fruit you create a perfect fruit tree. Perfect fruits sell for a lot of bells in other towns. I suggest you make a little forrest of them inside your town.
5. Certain bugs/fish can only be caught in certain seasons, so keep up or you're going to have to wait a year!

(both talking about your catalogue and museum collection)
6. Building a camping site (which is possible after the permit thingy) allows you to select through this campingsite which villagers enter your town. Until you have build this your town will fill up with random villagers.
7. It is possible to guide villagers that move newly into your town to a different spot by using the
plot reset trick.
8. The answers you give while on the train when first travelling to your town (when creating it) determine what your character's face looks like. The hair can be changed and so can the eye color, but the eye shape will always stay the same!
Alright, these were things that first came to mind and are things I wish I would've known when I first got it.
Have fun playing!