Make sure the frequency you want to use is clear. You don’t do this by mere listening but also by effectively asking if that frequency is in use. For example, on SSB after having listened for a while, ask ‘Is this frequency in use?’, followed by your callsign. If no response, repeat this question, followed by your callsign. If again no response, the frequency is yours to call CQ.
On CW and RTTY send ‘QRL?’. Some think a ‘question mark’ is sufficient. It is not as it can be confusing. If on a given frequency there is ongoing traffic (which you don’t hear), someone else on that frequency may interpret your question mark as if you are asking for the callsign of a station on that frequency. A ‘cop’ scenario may arise (see chapter 12).
‘QRL?’ cannot be misinterpreted by anyone, it means you want to know if that frequency is clear for you to use. A question mark in this situation is meaningless and may mean several things.

On CW you get possibly one of the following answers if the frequency is in use:

* R (Received-Roger)
* Y (Yes)

If by coincidence you landed on a ‘hot frequency’ (especially if used by a DXpedition or a rare DX station), chances exist you may get shouted at. Don’t worry, don’t react, just move to another frequency. Or figure out -by listening, not by asking- who the ‘DX’ is and work him.

Lots of problems can be avoided by following the first rule of operating (whether casual or DX): LISTEN. This golden rule used in combination with the magic word ‘QRL?’ will keep you out of trouble if you are looking for a clear frequency to call CQ.

* When calling CQ, don’t do as follows: call CQ ten times, followed by your callsign twice and then listen. Better to do this: call CQ twice and give your callsign ten times (I exaggerate, four times is sufficient!).
* The most important aspect when calling is not the word CQ, but your callsign. If conditions aren’t too good, it is important the station at the other side of the globe (yeah, cool!) hears your callsign rather than the word CQ. Too many times I’ve heard operators call CQ 15 times, give their call once, and then say ‘listening for any call now’. This is senseless.

Practice makes perfect. If you are not experienced, listen for a while to others to sharpen your teeth. You will quickly develop your own stye to make successful and pleasurable QSOs.