Are all interviews the same? If you've only been to a couple you might think so, but in fact there are all sorts of different interviews. Let's start by looking at the different types of interviews you might encounter:
One-on-one: Many interviews are still conducted one on one, though this is becoming less common in larger companies. It's more typical to meet two people, one from the relevant department (usually your prospective boss) and one person from the company's HR team.
Panel interviews: Very intimidating, panel interviews will see you facing several people, typically with a chairperson co-ordinating the questions. These are quite common in charities and the public sector, particularly where more than one person has to make the final decision.
Telephone interviews: Often used by large companies as a preliminary part of the process. Just because you can do this at home in your pyjamas doesn't mean you can treat these lightly. They will still be expecting the same sort of information that they would get face-to-face, so you have to prepare properly.
Group interviews: This is where several candidates are brought together at one time, and may be set tasks or asked questions in turn. There might also be a group discussion, or the chance to put questions to the other candidates. These are useful where employers are hiring more than one person, and teamwork and the ability to get along with others are key skills for prospective employees. The trick is to show that you can work with others, not that you try to dominate and put others down.
Sequential interviews: Again, more common in large companies, sequential interviews will see you meet with a number of people one after another. While you will often meet a variety of people with different skills, and thus might expect to be asked different questions each time, you may still find yourself answering the same question again and again. If this is the case, make sure to always give a full, comprehensive answer.
Progressive interviews: Finally, be aware that many companies will interview people two or even three times before they make their choice. You need to treat each one with equal seriousness.
Whatever process you might encounter, the requirements are the same. Do your research about the company, the people you are going to meet, and the job, and practice answering the sorts of questions you might expect to encounter.