Learned that French drains need a specific slope or they're useless
I was digging up part of my backyard to fix a soggy patch near the fence, and my neighbor came over to help. He told me French drains need at least a 1% slope, meaning a 1 foot drop for every 100 feet, or they just let water sit and clog up. I had no idea I needed to be that precise, figured a slight angle would do the trick. He showed me his setup with a level and a string line, it was way more math than I expected for a simple trench. Anybody else mess this up their first time and have to redo it?