Writing a press release, you will always found to be different task from a conventional content writing style.  It dose not happened to be a contemporary piece of writing but a restricted piece of work in first person narrative devoid of you and yours so it may not look like a piece of advertisement.     
Press releases are written for many reasons apart from the political ones, but as a fresher when you wish to start it like as service you can write about a wide areas and streams like  new product launch, upgraded products, a joint venture, a new top level hiring or promotion in a company.  Any thing exciting around you can develop into an excellent material for a press release.      
The writing style for a press release should be like as you are third person telling the world about a product or service. If you are producing content from a soft copy for a press release then you should go into like a statement rather than idea or personal view. A press release, if precisely said, more often should be in formal style of writing.