Free Money:
Check the dresser next to your bed. You'll find Grandpa's rainy day funds worth $1000.

Fall and Winter Crops:
Depending how you spell your name, you will have different crops to grow during the Fall and Winter. If you spell your name starting with a capital letter, you'll have Carrots and Eggplants. Leaving the first letter as lower case will get you Broccoli and Peanuts. If you put a symbol as the first letter in your name, like a heart, you'll be able to grow all 4 crops.

Extra Seeds:
If you start your game as a Girl instead of the Boy, you will get a bag of Grass, Turnip, and Potato seeds in your Tool Shed. You'll also receive the Watering Can without having to buy anything. You don't have to do anything special like start your name using a symbol or have a specific type of pet. The Boy player will never get free starter seeds, no matter how many symbols you put in his name or his pet's name.

Adult Cow:
Note: Boy only
When you're ready to buy cows, make sure you have 10000 G to buy two cows. Purchase your first cow and make the first letter in its name a symbol. Purchase a second cow and then don't start its name using a symbol. The first cow you buy will automatically be an adult and able to produce Medium Milk on its first day on your farm. Buying one cow and using a symbol at the beginning of its name will only get you a Medium Cow. Likewise buying two cows and using a symbol on each name won't get you two adult cows but two Medium Cows. Only when the first one starts with a symbol and the second one doesn't will this trick work.

Power Berries:
The berries give you more stamina points so you can work longer without getting exhausted. The more Power Berries you find, the more stamina you have. Inside your farm house is a flowerbox that shows you the number of berries you've found. If you only have found two berries, then there will be two pink flowers there. There are 10 Power berries:

One is given to you by the Harvest Sprites after giving them a few Mushrooms.
Behind your Wood Bin; till the soil from left to right.
Once you get the PickAx, use it in the left stoney-room in the Harvest Sprite's cave.
In the southeast area of your farm, before you get the field expansion in the 2nd year.
Next to the watering hole in the southwest corner of the field.
To the left of the watering hole along the eastern fence before you receive the field upgrade.
After your field upgrade, till the soil in the southeast corner.
Also in the field expansion area, till in the northeast corner.
When you clean out the first PickAx room, hit the wall between the two lights 6 times. You'll open a secret room and under one of the rocks is a berry.
In the secret PickAx room too.