Choose a task with a known answer
Your first session should not be a mysterious production failure. Pick a small bug, a missing test, or a contained interface change whose correct behavior you can describe. That gives you a baseline for judging suggestions instead of merely being impressed by activity.
Teach the repository once
Point Cursor at the local instructions, package scripts, and the few files that define the feature. Ask it to summarize the relevant path before editing. Correcting that summary is cheaper than repairing a confident change built on the wrong model of the code.
Close with evidence
Inspect every changed file, run the focused tests, and open the affected UI. Note where the agent needed help. Those observations become better repository instructions and better task briefs for the next session.