BREATHE. Before you DO or SAY anything. ALWAYS.
READ your state statutes regarding real estate practice. Within those statutes is everything you need to know. Have them handy.
KNOW your contracts. Understand what they mean.
That's a good start.

Do work smart and Don't take anything for granted

Do's and Don'ts for what specifically? Entire books could be written on this topic and still not exhaust it. 

every deal is different...and a "DO" on one could easily be a "DON'T" on another....

there's a surprise around every corner, in the real estate business...eventually, you'll have good instincts and make good business decisions based on common sense and "the golden rule".... you'll get repeat business, if you follow that advice...

School is just the beginning of learning which continues and continues.

To keep it short you get out what you put in. Know when to listen and when to speak. Answer your phone and return messages and emails quickly. Service is king

Best of luck and do only DOs.

Major DO'S - Learn your Contracts inside/out before you ever try to prepare one or teach your clients either. 

DON'TS - Don't go it alone the first few deals - at least until your broker lets you know you're ready to go solo.

Otherwise, seasoning takes many transactions under your belt - you will learn something from each and every deal for a very long time!

If you would not want it done to you ... then don't do it.

Know what you are doing or don't do it. Get help. Learning at anyone's expense is not a good thing. 

Do have a feel of your client and don't be afraid to turn down a listing or buyer. 

Do - Love what you do and do what you love - since it shines through!!
Don't - Count your chickens (or dollars) before they hatch (or before the transaction has closed)... 

All markets are different so have many talks with your broker.

Insist on working with very good people.

  These 4 posts may enlighten you:

   So you want to become a real estate agent by Kat Palmiotti 

   10 Things I wish I had known before I got my Real Estate License  Carla Black 

   Advice For New Agents

 You Need These People in Your Support Network

Do have a seasoned agent that you can contact with questions. It’s nice to have someone who’s willing to help you with the process while you learn. You’ll find that with time it gets easier and you’ll be writing contacts in your sleep.

Andrew,

I am not willing to write an encyclopedia of do's and don't.  Be ethical and you will find your way.  A

Put your clients needs first and ask for help when needed. Adhere to COE and learn as much as you can about the industry. Do not become a pompous, egotistical know-it-all! 

A travel brochure may wet the appetite or give you a glimpse but how could it capture an entire "trip" experience? Same with anything else too. The learning curve addresses your do's and don'ts quite nicely when you begin it

Your best friends or relatives forgot or do not want to share personal info. They went with another agent. 

One has to experience good and bad in order to learn and become proficient in whatever you do in life. 

Read the answer posted by Barbara Todaro !

Do = prospect every day

Don't = cash that commission check until you have it in hand

I am sure, your broker already gave you this list. Did or did not?

You learn from every transaction. 

I'd suggest asking your mentor/coach/trainer.  I'm sure the area specific ones will be more relevant to you than ones I could give you.

Do's:

1.  Be proactive and never assume things are being taken care of properly and timely at the other end.

2.  Live the golden rule

3.  Place the interests of your client above yours.

4.  Display a servant's heart

5.  Make a difference in someone's life everyday.

6.  READ, READ, READ, the primary source documents and contracts and know them inside and out!!!!  (example: if you are going to put in an offer on a HUD or Fannie Mae foreclosure GO DIRECTLY to the website and read the contracts and addenda for yourself!  Don't just rely on others because you are too lazy to do for yourself)

Don'ts:

1.  Take failure or rejection personally.  It is going to happen.  Learn and grow from it.

2.  Take shortcuts!  It will bite you in the end!!!

3.  Tolerate unethical or fraudulent behavior!!!

Best wishes for a long and successful career serving others!

ALL MAJOR 'DOs and Don'ts" !!!!

Now that is worth PAYING for.

I will give a couple.

1. VERIFY. 

2. Believe what you SEE not what you hear.

3. Don't take yourself too seriously.

4. Don't marry yourself to the outcome and trust a well conceived process.

5. Courage is daring to not conform. Will you be another smiley face in the sea of smiley faces?

First rule is treat your clients as you would want to be treated you are their advisor and counsel take it seriously and don't be affraid to ask those that know more than you do for help. Particularly your broker. 

If you need some help in N. Virginia I can help you

Don't Lie.

Tell the truth

As Nina said - that is a book of examples.    

Too long of a list to write here.  I would talk to other experienced agents.