For example, some states require that you notify that you're carrying a weapon and some don't.
What BigIron says about various states having various rules is absolutely correct so you should always know the law of your and any other state that you can legally carry in.
That being said even if the state doesn't have a law indicating that have to tell the officer you are armed, I believe it is both courtesy and prudent to do so while keeping your hands in plain view. The reason for this twofold.
1-These guys deal with liars and scum everyday and tend to be very suspicious both because it is their job and it gets them home to their family every night. They will be looking for signs of weapons. It is common courtesy to let them know you are carrying and ask them how they want to proceed for their safety. If nothing else it makes the stop a tiny bit less stressful for them and a less stressed cop is best for all parties.
2-If you do not tell the officer you are carrying and you do happen to print, show the weapon etc. then the officer is very likely to draw down on you because he or she doesn't know the score. You are also likely to be detained for the safety of the officer until they can figure out what is going on. This simply creates more stress for all parties involved and is not good.
Basically LEO's are people and some of them are a$$holes, just like a good portion of non-LEOs are a$$holes. Do not confuse these folks with your average everyday officer who is probably a bit high strung and deals with jerks all day every day. Most are good folks who have a high stress job where simple traffic stops can be the most dangerous. Making the situation as easy as possible for them is win win for all involved and may very well get you out of a ticket.
Be polite, be professional, be courteous. Keep your hands where the officer can see them and follow his or her instructions. If you feel the officer is overstepping their bounds, then be prepared to call a lawyer, tell them your basic info and then shut up. Follow the instructions of the officers and still be courteous.
Having a CCW permit means always de-escalating any situation IMO.
Oh if a LEO asks to relive you of your weapon, you may agree, you may disagree but if you don't comply things will get ugly for you.