What do Polonius's admonitions, beginning "And these few precepts," to Laertes and Ophelia in Act I, Scene iii, suggest about court life, and is it good advice?
Some of the most familiar quotations in the English language are found in Polonious's advice to Laertes and are considered good advice, among them, (1) "Neither a borrower nor a lender be" and (2) "To thine own self be true." He also advises his son (3) to be friendly but not overly so and (4) to listen more than speak.
As for Ophelia, she is harshly advised to "tender herself more dearly" when she confesses to her father Hamlet's affection (1.3.115). Polonius is afraid she will sleep with him, though Ophelia protests that "he has importuned me in an honorable fashion" (1.3.119-120).
As for what is says about court life, for men, they must meet standards of behavior that are above reproach. Women, well, they'd best be virgins ....
Here is Polonious' speech to Laertes (1.3.60-88)
And these few precepts in thy memory
Look thou character. Give thy thoughts no tongue,
Nor any unproportioned thought his act. 
Be thou familiar, but by no means vulgar:
Those friends thou hast, and their adoption tried,
Grapple them unto thy soul with hoops of steel,
But do not dull thy palm with entertainment
Of each new-hatched, unfledged courage. Beware 
Of entrance to a quarrel, but being in,
Bear't that th' opposed may beware of thee.
Give every man thy ear, but few thy voice,
Take each man's censure, but reserve thy judgment.
Costly thy habit as thy purse can buy, 
But not expressed in fancy, rich, not gaudy,
For the apparel oft proclaims the man,
And they in France of the best rank and station
Are of a most select and generous chief in that.
Neither a borrower nor a lender be, 
For loan oft loses both itself and friend,
And borrowing dulleth th' edge of husbandry.
This above all: to thine own self be true,
And it must follow, as the night the day,
Thou canst not then be false to any man. 
Farewell, my blessing season this in thee!
Towards Ophelia he basically tells her to be careful with Hamlet as nothing good will come out of it. It is not wise to continue meeting with him and he does not want his honor to be ruined. His daughter's honor as well, but firstly he does not want HIS honor to be ruined. As for Laertes, what he is trying to say becomes utterly confusing. Do this but not this. This but definitely not this. There are so many juxtaposing factors in this speech it is unsure what he wants him to fully do. But as Laertes goes to Paris he wants to keep him in check and give "good advice". The main 4 things he meant for Laertes was
1) don't borrow money but don't lend it either
2) Be true to yourself
3) Be friendly but don't be too friendly
4) Listen more then you speak