Without any doubt CW has key potentials for successful operation at any power level and it is worthwhile to give a few ideas about operating techniques. The major subject of this text is how to behave when QRO operators and QRP operators meet on air. It may be interesting to describe the different view points.
The most common power used in CW is probably 100 W or slightly less. Occasionally, this is called "barefoot". Many call this QRO operation, disregarding the fact there are plenty of stations who can use power levels of 1 kW or more. However, even most owners of powerful amplifiers work barefoot most of the time and save their energy (and trouble with neighbors) for pile-ups. The common terms are that RF output up to 1W is called QRPP while QRP is 5 W output power or less. This definition is widely defended by most QRP clubs, however, there is a lot of ham radio equipment that can deliver 10W output. Users of such equipment they claim to be QRP, too. In contesting the categories are different: QRP is 5W or less, LP ("Low" power) is up to 100W while QRO is anything beyond this.
For the sake of simplicity let us pick 5W as typified QRP and 80W as allegedly "average" power level denoted QRO in the subsequent text.
Most of all, let us not try to "judge" any op for choosing a power class which is not the one of our preference. All power levels have their advantages and disadvantages and all operators may undergo certain frustrations which are typical for the power level. The goal of this text is to minimize any frustration which may be caused by poor operating techniques.
Of course, a restricted power is an operational disadvantage, indeed. The most straightforward way to overcome the disadvantage is by optimizing antenna systems. If the QRP effect cannot be entirely compensated by more efficient antennas the operating skill becomes more and more important. It is worthwhile to study propagation. Many ham radio journals offer propagation forecasts, F2-layer models are widely available, and the Internet is an important resource, too. Since a nowcast is always better than a forecast it makes sense to check the cluster of the reverse beacon network. Without Internet access, a regular observation of the IPB beacons is recommended. The beacon dk0wcy delivers propagation information on air.
The QRO op wishes most of all that the qso partner can be read without too much effort. Let's face it, most operators may be willing to undergo considerable efforts to work "new ones" (typically new DXCC entities or other "rare birds") but few invest much to get one more station from more common countries like the US, Russia, Germany, or Italy. The implicit request is "Do not bother me with unreadable code". The QRP operator should acknowledge the fact that the station on the other end of the ray path has the more difficult task, i.e. to read the weaker signal. QRP operators will soon find out that their CQ calls are often overheard, and that it makes sense to watch out for CQ calls themselves. When a QRP op hears a CQ call a reasonable work hypothesis is that the calling station is using about 80W. Compared to 5W this makes up a difference of 2 S-meter levels. The QRP station must ask the following question: would I feel like answering this CQ call if it were 2 S-levels weaker than it is? If the answer to this question is a clear no it is better not to reply and watch out for another CQ caller. This is just a rule of thumb. If the CQ caller happens to use 1 kW he would hear you 4 S-levels weaker than you hear him, at leasts that's what the theory of wave propagation predicts. Yet, there may be some non-reciprocity to defeat this rule. The general advice is that a little try may not do much harm, but do not insist or feel frustrated if you fail when trying your luck.
It may happen that the QRO station has to copy real weak signals. In this case, the QRP op should grant the QRO station the leadership over this QSO. The QRP operator should listen carefully to the requests and instructions of the QRO station. It it asks something like "NAME?" the answer should be something like "PETER PETER PETER KN" instead of a lengthy over including much overhead. The QRP op should refrain from overloading the call by a /QRP extension, at least a repetition of this extension should be avoided. Please do not record the extended call in a memory keyer. The /QRP extension may make some sense when calling CQ far away from traditional QRP frequencies but in most cases it is more burden than gain.
The QRO operator has a right not to be exposed to poor code, i.e. the QRP operator has to make sure to transmit well formed and error free code with precise character spacings and generous spaces between words. The QRP operator should send slower code than the QRO station.
The QRP operator should respect directed calls. Do not answer CQ DX if you are not DX, do not answer CQ SKCC if you are not SKCC, even if you do not know what SKCC means. If you are blunt by nature and if you have reason to believe that the caller has a good and generous heart, and if you think you may override the directed call by your answer, at least keep your call short and give the caller a chance to overhear you.
QRP ops should be more patient and more tolerant than others, they should not police anyone for calling CQ 3 kHz away from a QRP frequency. Likewise, QRO operators hardly abuse QRP calling frequencies since they are mentioned by the band plan which is respected by all decent radio amateurs.
Last but not least the QRO station expects any QRP op to have an above average operational skill. A decent QRP op is expected to know the relevant shorts and Q-codes such as QRK, QSY, QSX, QSV, QSZ, etc.
The QRO station should acknowledge that QRP is a legitimate choice, at times imposed by factors beyond the control of the QRP station such as the lack of resources, or an oversensitive RFI environment, or restrictions from 3rd parties. Keeping this in mind, a QSO partner should always show the good will to finish any QSO. Formally it takes no more than the exchange of calls and reports to finish a QSO.
The QRO station should give honest RST reports. Especially the R number is crucial. R4 means to be able to copy without difficulty. If you consider a signal hard to copy you must tell and give R3. If you anticipate problems be honest enough to give R2. If you feel unable to copy the call it is ok to reject the QSO giving R1 or QRK1 which is essentially the same. If the QRO station sends a stereotype RST 599 or even a 559 the QRP is authorized to believe that the R5 means that the QRO station has indeed an armchair copy.
QRO stations should keep a reasonable distance from the QRP calling frequencies, at least for CQ calls.
While the band plan mentions the calling frequency and while these are well-respected (at least weekdays) the band plan does not give any hint about preferred places for QRP. In practice, QRP stations tend to settle around the calling frequencies (nn060 kHz on 80/20/15/10m) with the tendency to stay between the calling frequency and the upper band end. QRO stations working there should be prepared to be called by QRP stations. If a QRO station feels annoyed and molested by QRP it may wish to avoid these frequencies.
QRO operators with a generous spirit should occasionally check the preferred QRP frequencies and answer cq calling QRP stations using QRP themselves because QRP operators are especially fond of two-way QRP contacts.