POLONIUS (continued) 

And these few precepts in thy memory
See 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 to thy soul with hoops of steel;
But do not dull thy palm with entertainment
Of each new-hatch'd, unfledged comrade. Beware
Of entrance to a quarrel, but being in,
Bear't that the 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 express'd 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 dulls the edge of husbandry.
This above all: to thine ownself 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!


Henrik Ramel
Ramel was a Danish diplomat, born in Poland sometime in the 1550s. Notably, he appears in Wikipedia only in Danish! He is mentioned in Keith Brown's essay on the play in English Studies Vol. 55 (1974). 

Precepts for the Well Ordering of a Man's Life
William Cecil, Lord Burghley, wrote these for his son Robert before HE left for Paris in about 1584. You can read the entire set right here, but the ones that are particularly interesting for their parallels to what Polonius says are as follows:

Precept V - Be sure you keep some great man always to your friend, yet trouble him not for trifles; compliment him often, present him with many, yet small gifts, and of little charge, and if you have cause to bestow any great gratuity on him then let it be no chest commodity or obscure thing, but such a one as may be daily in sight, the better to be remembered…

Precept VI - Neither undertake law against any man before you be fully resolved you have the right on your side, which being once so ascertained, then spare neither cost nor pains to accomplish it. 

Precept VII - Beware of suretyship for your best friend

Precept VIII - Towards your superiors be humble yet generous; with your equals familiar yet respective; towards your inferiors show much humility, with some familiarity…

Precept X - be not scurrilous in conversation, nor satirical in your wits… jest when they do savour of too much truth leave a bitterness in the minds of those that are touched.