For either method, drain and remove tofu from package. Make sure you are using firm or extra firm tofu.
Method 1: Storebought Tofu Press
Place the block of tofu in the press. Tighten slightly.
Place the press sideways over a wide bowl or towels to allow the tofu liquid to drain out.
Every 5 minutes or so, tighten a few more turns and flip the press over so the tofu drains from the other side. (Tightening too much too quickly can cause the sides of the tofu block to bulge.)
Press for a total of 30 minutes. If pressing overnight, let the tofu continue to press and drain over a towel or bowl in the fridge. You do not need to flip during this time, but tightening a few turns here and there will help.
Method 2: DIY
For this method, you can leave the block of tofu whole or cut into slices. I prefer to slice for the best texture.
On a flat surface like a cutting board or sheet pan, lay down a folded lint-free towel or cloth. You can also use paper towels. Place the tofu on top, followed by an additional towel, then another cutting board.
Place something heavy on top of the cutting board. I prefer to use a cast iron pan. Other options are canned goods or a stack of hefty mixing bowls. Anything to add a decent amount of weight! Don't put so much weight that the tofu gets smushed. Gradually add weight if you are unsure.
If the towels become saturated, replace them.
Press for at least 30 minutes. If pressing overnight, place in the fridge.
Notes
30 minutes is typically the minimum of time to press tofu. I prefer to press for about an hour.