Remember. CW is style and precision and, above all, a way of behaving, so:
1. always transmit at a comfortable speed, allowing you to make the lesser number of errors you can make.
2. always greet the correspondant, thank for the information received and answer to the questions made to you.
3. always lower your transmission speed to match the other station, if its slower than you. If the correspondant is faster than you, do not be ashamed to ask for QRS.

A QSO/DX in CW is three-folded:

• Uses abbreviations (Q code).
  
• Uses Procedural Signs (Prosigns).
  
• Is structured.
  

of course, you might decide to have a rag-chew QSO and enjoy the full pleasure of a CW free talk. This will allow you to taste the unique flavor of CW ....

Hereafter is a list showing the main Q codes and Prosigns (in bold).

QTH: the station location
PSE: Please
AR: is used when the QSO is not yet started, it is an invite to transmit.
TNX: Thanks
FER:  For
UR: Your
HR: Here
CQ:  used to call stations locally or worldwide
SK:  end of transmission
HPE: hope
CUAGN: See you again
73: Greetings
K: used in an ongoing QSO, it is an invite to transmit
KN: used in an ongoing QSO, it is an invite to transmit only to the called station
GM, GA, GE: Good Morning, Afternoon, Evening
BT:  sentence separator
OM: Old Man
ES: and
QSB: evanescence
QRM: reception is disturbed by other stations
QRN: reception is disturbed by atmospherical noise
HW:  how (should be followd by ?)
INFO: information
RPRT: signal report
DR:  dear
OP:  station operator, often used instead of NAME
RIG:  transceiver
ANT: antenna
PWR:  output power
WX: weather condition (CLOUDY, SUNNY, CLEAR)
TMP: temperature
HR: here
BK: break, used to pass back the key to the other station without explicitly repeating its callsign
R:  received
FB: Fine Business
VY: Very
TU: Thank you
QSL:  can be referred both to the confirmation QSL card or as K ("understood"). Confirmation QSL can be asked VIA BURO or VIA DIRECT
QRS:  invitation to transmit slower (shoud be never necessary to ask for it)
QRQ:  invitation to transmit faster (for real, real fun !)
AGN:  again, please re-transmit last message
SRI: Sorry
GL: Good Luck
GD: Good

Bold signs are Procedural Signs (Prosigns) and they are intented to be the QSO control signals, they must be transmitted as a whole character (e.g.:  KN _._ _. ).

The correct CQ call is:

CQ CQ DE IZ0FYL IZ0FYL AR

while ending with K:  CQ CQ DE IZ0FYL IZ0FYL PSE K    is formally incorrect, in this call there are two mistakes:
- K must be used only when the QSO is estabilished
- PSE is redundant, since the prosign AR is an invite to transmit itself.

The answer to a CQ is :

IK0YGJ DE IZ0FYL AR

note, again, the use of the prosign AR. If you are sure that the correspondant is copying you, you might use PSE K instead of AR.
Now, the first station can call explicitly the responding one, and pass back the key using K:

IK0YGJ DE IZ0FYL GM OM TNX FER CALL BT UR RST IS 579 QSB BT MY QTH IS ROMA ES MY NAME IS LUCA BT HW ? IK0YGJ DE IZ0FYL K

It is common use to repeat two times NAME and QTH. The words IS,  ES are actually optional.

The correspondant has been asked HW ? and received some information (RST - please send the real one, not just 599 !) so a correct behaviour would be to thank for the information received and give back the same information:

IZ0FYL DE IK0YGJ BT GM DR OM CARLO TNX FER RPRT BT UR RST IS 569 BT QTH ROMA OP CARLO  BT MY RIG IS FT 817 PWR 5W ES ANT IS VERTICAL BT HR WX IS SUNNY TEMP 10C IZ0FYL DE IK0YGJ K

now suppose that the correspondant lost something because of QSB, he might ask again for the lost information using the prosign BK (notice: when using BK using DE + your call after is optional)

BK DE IZ0FYL PSE UR PWR IS 5W ? BK

BK DE IK0YGJ R  MY PWR IS 5W BK

do not be ashamed to ask again (always PSE) if something goes wrong:

BK DE IZ0FYL ?? SRI QRM PSE AGN BK

in this case, it is imperative to repeat slowly for 2-3 times the lost information
 
BK DE IK0YGJ  R MY PWR IS 5W PWR IS 5W PWR IS 5W BK

after receiving the information, always remember to thank for it and the QSO might go on:

BK DE IZ0FYL R R TNX FER INFO VY FB UR PWR ES 5W QRP BT MY RIG IS FT 817 PWR 5W ES ANT IS DIPOLE BT HR WX IS CLOUDY TEMP 12C IK0YGJ DE IZ0FYL K

at this point the QSO often closes, after the necessary greetings:

 IZ0FYL DE IK0YGJ DR LUCA TNX FER INFO ES FER QSO MY QSL VIA BURO BT IK0YGJ DE IZ0FYL 73 ES HPE CUAGN TU SK dit dit

the QSO is usally ended with the "two bits" (dit - dit),

BK DE IZ0FYL TNX FER VY FB QSO DR OM CARLO MY 73 GL ES GD DX IK0YGJ DE IZ0FYL 73 TU SK dit dit

If you prefer so, you might add a notice of color to acknowledge and respect different cultures, here is a selection of words in some languages I use to end the QSO:
- CIAO (greetings, italy)
- HVALA (thanks, Yugoslavia)
- SPACIBA (greetings, Russia)
- SKAALA (cheers, Scandinavian)
- A BIEN TOT (greetings, France)
- TSCHUSS (greetings, Germany)
- ADIOS (greetings, Spain)