I just sold my version of this game on Ebay as I was addicted. Some advice:
* Get on WiFi as soon as possible (try the Facebook Animal Crossing Addicts group to share internet friend codes with people from the UK). You can then pick different fruits from other people's towns and plant them back in yours. The advantage of this is that Nook (the g*t) only pays £100 for your native fruit but a whopping £500 for non-native. When you've been playing a while, grow all non-native fruits and rake it in.
* One of the rocks in your village will give up 15000 bells if you hit it with your spade. It's a different one every day. I recommend you dig a hole behind and to the right of yourself before whacking it because then the action won't throw you off (you have limited time to get all the cash out).
* Catch bugs with the net (esp around dusk when you get them on trees and coconut trees - they're cash-rich bugs) and catch fish with your rod. Fish in particular can help you rake it in as some are worth an absolute fortune. If you want to fill the museum quickly though, remember to give the first of any species to Blathers.
* Dig up the dodgy looking bits in the ground for fossils for your museum. If you already have one, Nook will give you lots of cash for it. Similarly, if it's been raining the night before there will be loads of buried Droid things - they are worth a fortune.
* write to each of your villagers every day and attach a gift (something pants will do like a cheap shell or fruit) - they will send you something back which will normally be furniture which you can stick in your house or sell for hard Cash.
* Get the golden shovel by burying your shovel for 24 hours and then digging it up again!!
* Buy all the flowers in Nook's shop every day and plant them all over your village. Water the brown ones each day so they don't die. When you have enough scattered around Pelly will tell you in the Town Hall that your town is ace. When you've had Perfect Town status for 15 days you'll get the Golden Watering Can.
* Make sure you pull up weeds (the little green sticky up bits) regularly.
* Shake every tree in your town each day to get at least 2 items of furniture and some cash. You will probably disturb bees. Try to catch one in your net - it's worth 4000 bells. If you can't you'll get stung. Restarting the game after saving loses the sting mark although if you don't mind the other villagers laughing at you it doesn't make any difference.
That's probably enough for now - ask me if you have any questions!
(Can you tell I was an addict?!)