A number of books I have read and tips from traders say you should only invest in a company if you understand it and how it makes money. This is one of the reasons Warren Buffet didn't invest in Tech stocks as he didn't understand how they made money.
For some industries this is a little easier, but for others, the industry is foreign to a large number of investors and so to are some of the idiosyncracies that can really affect an organisation.
For example, some people may not understand or easily see the link between the direction of the overall markets and those companies that generate revenue from managed funds or superannuation especially if that company, such as AMP is also involved in a large number of other activities, but can easily see how it would affect Listed investment companies such as ARGO.
For the particular companies you are interested in, how did you learn what you needed to know to understand the company, how it makes money and what factors, both internal and external have an infact on it's share price?