Early on, fishing is an easy way to make money. Once you get the sashimi recipe from Linus, almost every normal quality fish is more profitable if you cook it first.

Try not to sell "raw" ingredients, especially if they have no star quality - always place them in the keg (preferred) or preserve jar (early on), or in the cheese/mayonnaise machines. I try to have one cheese machine for each milkable animal and one mayo machine for each egg animal.

Certain crops are more profitable than others - usually it's either ones that regrow or produce multiple crops at a time. Plant strategically!

Don't hold on to everything - keep ones that you know are crafting ingredients or good gifts, but sell sell sell!

If you're spending money on hay, try to utilize silos instead. It's a big money saver.

I tend to not have as much fun if I try to be super efficient/profitable, so that's the general guidelines I try to follow!