Most countries — including China — require that journalists be accredited, and carry a press ID. This is not the case in the United States, where our Constitution guarantees press freedom from government interference. In the US, all a journalist needs is a business card or a company photo ID.
For most of the reporting I do, all I need is a telephone — I haven’t yet had anyone not believe I was who I said I was.
When I go out to interviews, I bring my business cards. They suffice for 95% of the stuff out there. Some publications and TV stations issue photo IDs to their employees. They can also be used for identification.
For special events, etc… I write an assignment letter on company letterhead for my editor to sign, and fax it or mail it to the appropriate agency, with a photograph if required. They issue me a press pass for that event.
For ongoing special coverage — police, military affairs — I need that assignment letter and photographs and get a more permanent press pass.
Some countries accredit foreign journalists — again, you need a letter from the editor. When I worked in the ex-USSR I had to check in with the Ministries of Information and get accreditation.
In China, I have the standard journalists’ accreditation, which took several months to get.
There are also associations that issue press membership cards — for example, in the United States, the Society of Professional Journalists issues a membership card.