Look you, sir,
Inquire me first what Danskers are in Paris,
And how, and who, what means, and where they keep,
What company, at what expense; and finding
By this encompassment and drift of question
That they do know my son, come you more nearer
Than your particular demands will touch it.

In this quote from Act 2, Scene 1, Polonius gives his servant Reynaldo directions on how to spy on his son in Paris. Polonius’s motivation for doing this are not entirely clear, and it’s possible that he just wants to be sure that Laertes doesn’t get into any trouble in France. But regardless of his motivation, sending an agent to spy on his son taints the character of Polonius and lends credence to Hamlet’s assessment of him in Act 3, Scene 4 as an “intruding fool.” You can read more about this quote in Quotes by Character: Polonius (the first quote).

See you now,
Your bait of falsehood takes this carp of truth.
And thus do we of wisdom and of reach,
With windlasses and with assays of bias,
By indirections find directions out.

Later in Act 2, Scene 1, the scheming Polonius uses a colorful fishing metaphor as he provides further instructions to his servant Reynaldo on how to spy on his son Laertes in Paris. The more Polonius talks, the more he reveals himself to no stranger to intrigue, which might be why King Claudius (who is no stranger to intrigue himself) values him as a close advisor.

The explanation for this quote in Quotes by Character: Polonius (the second quote) discusses how both large and small incidents of intrigues and deceptions abound throughout Hamlet.