Making straight, accurate cuts in big sheets of plywood or MDF can be challenging. Even if you have a table saw, it’s ill-suited to the task. That means the tool of choice is a circular saw.
To get better results, you need a saw guide. You can simply clamp on a long, straight board and use that, or you can purchase a clamp-on edge guide. Both work well. Just make sure you measure correctly to accommodate offset of your saw — the distance from the edge of your saw plate to the blade. You can also use a guide that you mount your saw on. The one we use most has an arm with a measuring scale, as well as guide that follows the edge of the plywood. That makes it easy to set up and use.