Installing a spoilboard will go a long way in making sure your cuts are clean and level. A spoilboard is a removable work surface mounted to the top of the router table which protects the table from damage as the router bits cut in and through the material. Once installed the spoilboard will need to be surfaced using a Spoilboard cutter or Endmill to make the surface flat and parallel to the X and Y travel. It is generally a good idea to resurface (bottom clean) often as the spoilboard surface may become uneven over time and clean up any gouges or cuts.
The EURO STYLE CLAMPING JIG is a free project available on the Next Wave CNC website that not only provides templates and files for creating a clamping system on your CNC machine but also steps for creating and milling the surface of that spoilboard.
There are many different layouts for spoilboards and they can be as intricate or as simple as you need them to be. I would encourage you to search the internet for a layout or ideas that will fit your machine and the projects you would like to make.