Where should I aim my first volley when I approach the net?
The short and easy answer is crosscourt. Naturally, being tennis, the short and easy answer is only a small part of the story which always has many variables to consider.
Our job as coaches is to try and simplify the answer and then let you, the player, go out and experience the variables and learn what works with your given skills. Therefore as a general rule crosscourt is king if angled wide enough to avoid the opposing net player. A clear guide is bullet-pointed below.
If the return is low at your feet try volley low crosscourt with a sharper angle since the opposing net player will be looking to intercept.
The higher skilled player can spot an opponent moving to cross and redirect the volley down the line. Remember even pro players find this volley tough to play at the last second.
An average height volley is definitely a crosscourt volley. Try strike firmly and reasonably deep.
A high volley can be aimed both ways but unless confident of a winning line volley stick to a strong crosscourt volley.