To keep the edge from risk of shattering, I use a straight edge and sharp knife to carefully cut along the line before using a power saw. That way the edge is already cut clean before any saw blade teeth get near to it. I do that with any cut where I want a clean edge. - TedBear
The best tips I can offer you are to cover the area you are cutting through with tape on the top and bottom of the timber. This helps prevent the timber fibres from blowing out.
You also need to set your saw blade depth to only fractionally deeper than the thickness of the timber. This ensures that more than a couple of teeth are cutting the timber at any one time. If the blade is set too deep, fibres are splintered and pushed out the face of the board. I've created a rendering below for you to illustrate it better. - MitchellMc