Using a sharp knife can ensure a smooth chopping experience.
Avoiding crushing helps to prevent less acid from being released.
You should also try to begin by cutting off and throwing away any little bit of root end, which has lots of stringy little roots hanging from it.
This method will allow most of the noxious sulfur compounds, which are found in the root, to escape.
Next, you can remove the pointy tip of the onion, peel its skin and slice it with fewer tears.