You can get extra money by plowing the ground. When you find money remember that location plow it again the next day. This only works once a day. Put a fence on top of where you plowed, then take it off so you can plow again.
Water a big mushroom (right above a big mushroom where a piece of wood is sticking out) to refill your water can. This is useful when you are not near a pond. Note: This trick only works if you have a watering can because the sprinkler does not need to be refilled. You can also refill your water supply by watering the rocks in the left room of the Harvest Sprites' home.
Choose to be a girl character to receive extra crops and seeds.
Obtain a watering can and water an egg that is near the shipping box. It will turn into a fence. Pick up the fence and it will change into an egg. However, the fence will remain allowing unlimited eggs to be obtained.
Go to your chicken coop. Put all your eggs in the shipping bin. Stay in the chicken coop. Turn off the Game Boy, then turn it back on. You will be in your house. Return to the chicken coop. Eggs will be there and it will also be the same day. Repeat this as many times as needed to get money each time. Note: This does not work with the cow's milk.
During the first day, go to the drawer in your house. Face the drawer, and press A (when you do not have a tool in hand). A message stating that Grandpa left some gold before he died. You will get 1000 G.
When something is bought, buy as much as you can afford so you do not have to buy the same item again when it runs out. Only ship crops during the day, and feed and water everything at night.
Use the following trick to get that middle crop square. Before you plant seeds in that square tilled soil just throw a rock in it, so you can get to all of the seeds/plants. Note: If you have the umbrella it would be easier to use it instead.