Square Your Saw Blade
You can't make clean cuts unless the blade is square to the saw's bed. Most saws have an adjustment screw near the angle gauge for this purpose. With the saw unplugged and the blade set to maximum depth, retract the blade guard and hold a square against the bed and blade to make sure they're exactly 90 degrees to each other. Adjust the screw if necessary.
Next check to make sure the blade is parallel to the saw bed. With the saw unplugged and blade fully extended, hook a combination square or Speed square on the back of the bed and slide it tight to the blade. They should line up. Most saws don't have adjusting screws for this. Make adjustments by carefully bending the bed sideways until the blade and bed are parallel.