A major rule of PCB design which always missed by beginners is to lay out your board on a fixed grid. This is called snap grid, as your components and tracks will snap into fixed grid positions. 100 thou is a standard placement grid for very basic through-hole work, while 50 thou is a standard for general tracking work. For even finer work, you may use a 25-thou snap grid or even lower.
Why is a coarse snap grid so important? That’s because it will keep your components neat and symmetrical. Besides, it makes future editing, dragging, movement and alignment of your tracks, components and blocks of components easier as your layout grows in size and complexity.
Enough PCB layout practice is very crucial for your future. You’re required to start out with a coarse grid like 50 thou and use a progressively finer snap grid if your design becomes tight on space. Drop to 25 thou and 10 thou for finer routing and placement when needed. This will do for 99% of boards. Make sure the finer grid you choose is a nice, this means 50, 25, 20, 10, or 5 thou is a good choice.