Doing photography on purpose whatever it is is to be "on assignation" meaning there is a task (subject), there is a medium (photo), there is a follow up (by diffusing and sharing your pictures). So be on assignation is not a so call professional or strictly journalistic affair. It can involve everybody under some specific circonstances. This is why every types of photographic devices are pertinent to use on assignation assuming the fact they are available and fully operational. For sure the final purpose of your pictures may dictate some technical considerations in doing the choice of your equipment.
Working with photojournalists during several years I had the chance to observe, develop and apply a personal approach regarding on assignation mandates. During the film era it was almost impossible to verify on place your production output except in using small low resolution instants photographs done with Polaroid tests. Now digital photography allows us to do post-check on the spot and to correct or repeat your results almost instantly. On the other side the time between picture taking session and transmitting them has been reduced considerably and post-production opportunities are less available to photographers. Many automated photo correction softwares are now designed to respond to that new demand but often with the prejudice of preventing more original creativity.
Here are some mottos that I have develop over the years when I am planning a photo project:
Be prepared (materially) meaning be in shape, wear the right clothing and equipment including your back up material;
Be introduced by having the contact, the good credential and by assuming the right follow up with people involved;
Be documented, knowing your subject and its last development may be capital for your approach;
Be smart and stay aware of the context of your subject;
Be result oriented by acknowledging your needs or the needs of your mandate;
Be persistent and make sure to plan some back-up production;
Be aware especially about any security manner about the context you are working;
Be versatile to any in place adaptation or change of your planning;
Be systematic and make sure you follow most if not all your requirement;
Be sensitive about your subject since it can oriente your creativity to new directions.
And be prepared to invest yourself again and again because you will have the opportunity to learn, try and achieve new ways to fulfil an assignation. Even after these past years to have a certain amount of different assignations I am still ressenting the excitation (and by extension the insecurity) of doing a new assignation or photo project.
Lastly every photograph can develop its own style or signature from its own experiences. It is only a matter of believing on his or her ability to do so. Creativity is not an "elite" prerogative of the few but a basic characteristic of all the humanity and others living things.
We do photography on purpose (even for ourself) and doing photo projects may be one of the best way to illustrate that simple fact.