Harvest Moon Back to Nature - Upgrade Tools

This is another tip when you're thinking about upgrading your tool(s) ...

Don't upgrade your tools

^_^ Weird, isn't it? 

I'll take one example: watering can.

So you need to use your watering can until it reaches 400% You can check this by hitting the 'start' button, and move the arrow to right until you find the tools section: check the percentage. When the watering can reached 400%, it's time for you to go to the mine and get a Blue Stone. Take it to Saibara, talk to him, pick the 'upgrade tools' option. He'll need three days to upgrade your watering can. 

I hope it helps. I think you'll be saving a lot of money & time if you use this, rather than using the conventional upgrade ^_^