Untreated wood surfaces turn up black marks when water puddles on them over a period of time. Oxalic acid will get those black marks out. Barkeeper's Friend is the thing to use as it has oxalic acid. Make a milky paste of Barkeeper's Friend and water and set it on the marks. Let it sit for at least five hours. When you come back to it the marks should be gone. In some cases it may need a second application.

Note: The acid may whiten the wood. This is definitely not a strategy for fine woods. And on any wood, be sure to wipe up the paste on any areas outside the region of the black mark.

Here's some ideas from the gas company on how to save energy while washing clothes. Centerpoint Energy suggests that you can wash all your clothes in cold water because modern detergents work fine in cold water. That would be a big savings. Also, wash during the morning or evening so that your washer adds heat to the room when it's most needed.

In your fridge and kitchen cabinets, try installing revolving turntables for easier access to items that normally sit in the back. ​https://blog.nationwide.com/spring-cleaning-tips-and-tricks/

Here's an easy one. Use an all purpose cleaner like 7th Generation's to damp wipe the insides of your trash and kitchen garbage and recycling receptacles.