what is some advice Polonius gives to Laertes? act 1. iii.

Give thy thoughts no tongue, Nor any unproportioned thought his act.
Don't give away what you are thinking so easily.
Line 61

Be thou familiar, but by no means vulgar.
Don't try to be popular. Just be cordeal.
Lines 62-65

Those friends thou hast, and their adoption tried, Grapple them to thy soul with hoops of steel; But do not dull thy palm with entertainment Of each new-hatch’d, unfledged comrade.
Keep your good friends close. Don't be friends with too many people than you can really know.
Lines 65-69

Beware Of entrance to a quarrel, but being in, Bear’t that the opposed may beware of thee.
Stay out of fights. If you choose to enter in one, make sure they know you mean bussiness.

Neither a borrower or a lender be. Don't borrow or lend money or you will loose the money and friends.