A good reading has a shape: open with the chart's overall structure, name the big three, take the two or three loudest placements, add the tightest aspect, and close with the current transit. Twenty minutes of material, delivered in that order, sounds coherent to someone who knows nothing about astrology.
The ethics are simple and non-negotiable. Do not predict death, illness, or pregnancy. Do not tell anybody to leave a relationship or a job. Do not read for someone who has not asked. Astrology is offered for reflection and entertainment, and it must never displace medical, legal or financial advice.
The best habit a reader can build is describing rather than deciding. 'This placement often shows up as X — does that land?' invites correction. 'You are X' invites either flattery or offence, and teaches you nothing about whether you were right.