Every beginner makes these mistakes. Here's how to stop making them.
1. Moving the same piece twice in the opening — develop all your pieces before moving any piece a second time. 2. Ignoring king safety — castle early. 3. Not controlling the center — the center is the most important area of the board. 4. Trading pieces without a reason — every exchange should serve a purpose. 5. Not looking at your opponent's moves — always ask 'why did they play that?' 6. Playing too fast — use your clock. 7. Not analysing your games — review every game, win or lose.