Mine defaults to New Selection also IF there has been no selection made already.

I zoom in a lot and make more points where needed with the Polygonal Lasso Tool. That in combination with the space bar to pan around the image. Backspace removes the last points made if I mess up. I still have the 4 option icons at the top of page. I flip back and forth with Add to Selection and Subtract from Selection.

Whichever way it works best for you is the right way to do it.