Nothing affects the quality of your analysis more than where the phone stands. Learn this once and every session after it benefits.
Behind the baseline, on the centre line. Set the phone behind one end of the court, as central as you can. A fence is its natural home.
Higher beats lower. Aim for head height or above. A phone at ankle height watches players hide behind each other. A phone raised on the fence sees the court laid out properly.
Landscape, always. The court is wide. Turn the phone sideways and let the frame match it.
Both baselines in frame. Glance at the preview: near baseline, far baseline, net between them. A little sky is harmless. Cutting off the far end of the court is the one real mistake, because play the camera cannot see is play that cannot be analysed.
Steady over perfect. A mount is nice. A phone wedged firmly against the fence is just as good. What costs you is movement: a phone that slips, tilts or takes a knock mid-session. Wedge it properly, then forget it exists.