To start with, the core thing that all of the managers should know is that there are two completely different methods of software development: waterfall (cascade) method and agile (flexible) method.
These techniques are the most popular ways of software development nowadays.
So, the main topik that project managers should remember is that both cascade and flexible manners are different and each have positive and negative sides.
Agile methods pluses — are the week points of waterfall one and vice versa.
Agile philosophy guarantees that the development process will be transparent, fast and very flexible. The team will show first results to the clients extremely fast. Also, the agile developers work is to include the coolest features offered by clients to the project, to always have a feedback and, if necessary, to change product seriously. This flexibility lowers the risk to do something that will not be popular and commercially successful.
On the contrast, waterfall or cascade way is too formal, typed and not flexible. Which means that the clients quates will not be heared and that the clients will see only the final version of the product when it is too complicated to change something — well, this will made the product development not clear enough. In addition, this way of developments is more expensive and long.
From another side, waterfall method allows to have a clear documentation, simple project structure, which is easy for not experienced teams. Cascade way also allows the projects owner to track the financial risks and the resources spent on the project: time and money! On the contrary, the agile project needs the team to be experienced and client-oriented. Moreover, with new and new claims the project have a risk to have never been finished. Also, it is completely impossible to predict, how many resources do you need when the project is always changing.
In conlusion, all the techniques are cool in right place! If you have a startup, users of your service are interested in it and take part from the real beginning, you are not completely sure which functionality will you need from the project and the developers are professional and unite — agile is your choise!
But if the client do not want to take part in product development, he has got specific demands and he is ready to spend a lot of money, the waterfall system will be better.
Well, if you will learn these two conceptions your IT project management skill will increase steadily!