To design your own maze by hand, start by choosing an overall shape for the maze, and then create contiguous paths and junctions that link an entry point on one side to an exit point on another side. Alternately, use sites such as DiscoveryEducation.com to automatically generate a maze.
Creating a maze by hand requires maintaining a consistent path width, which allows you to keep the maze uniform and easy-to-view. If the maze has wide paths in one area and narrow paths in another, it makes it much harder for you to keep track of the different twists and turns and more likely to accidentally create an unsolvable maze.
Practice drawing different paths on a scratch sheet of paper to build up your skill before working on the final maze. Also make sure to incorporate different types of junctions, which are points in the maze where the path diverges. These divergences allow you to fill areas of the maze with dead ends rather than force one path to wind throughout the entire area.
The maze creation tool on DiscoveryEducation.com asks you to choose an overall maze shape and size along with other aspects. After defining the look and feel of the maze, the tool automatically generates the paths and junctions and allows you to print out your maze.