I've been a fan of Erik Kennedy's work for a while now, but he's really outdone himself with this Twitter thread. He's up to almost 30 UI/UX design tips so far, and he's delivered a LOT of value here.
One of the things I appreciate about Erik is that he's able to boil down the act of making artistic choices in such a way that they seem approachable, even for non-artists. He covers a large range of topics here, from positioning screen elements in a clean, understandable way, to making font and text choices, to designing color palettes -- including gradients.
If you ever find yourself without professional design help (or if you ARE that professional design help) and need to move a project forward, I really can't recommend this enough.
Great work, Erik!