Instructions
Create simple levels. Levels that are very complex keep many people away. Come up with one idea for the level and tweak the pieces that make up the idea to make a cool level.
Design a theme for the level. Have all of the pieces on the screen match. One of the worst levels to play is one that is a mishmash of all sorts of colors and themes without any cohesion.
Build a level that is not linear. Design the level so that the main character has to move all four directions and use the Z-Axis. This adds depth to your game.
Add multiple ways to complete a level. People think very differently from each other. Create ways that make the levels completable in a variety of ways.
Use different materials. Use wood and metallic materials for different pieces in the game so nothing looks identical.
Test your level. The more you test your level, the more things you will find that need to be fixed. You will also come up with new ideas as well.
Build the level taking as much time as you want. There is no time limit in making a level, so do not rush through it. The more time you take in placing pieces and designing the level, the better the final outcome will be.