I remember taking my IQ test pretty well. I can't remember the name of the School Psychologist, but I recall that it was a middle-aged man with a beard and a sweater (for some reason, every male school psychologist I've ever met eventually developed a fondness for sweaters and beards) and I remember some parts of the test. I also remember thinking that I did very poorly.
Don't misunderstand that last part. The gentleman who administered the test was a warm, friendly kind of guy and definitely encouraged me, but there is a funny thing about taking an IQ test; they don't stop until you get a lot of questions wrong. I put together some puzzles and then suddenly, there was one that was way too hard. The next one was even harder. I became aware that I was getting a lot of them wrong and, being a smart kid and not at all used to messing things up, I was starting to get upset. In giving a test, however, it's important to get a picture of how much a student can do. This means that testing does not stop until a student hits a "Ceiling," usually three to five questions in a row wrong. A lot of psychologists I know will warn kids about this by pointing out that tests are often given to kids over a wide age range, so they shouldn't worry if they get to the end and they get the last few wrong ("those are for high school or college kids").
Aside from hitting a Ceiling though, I can say that taking an IQ test is usually fun. The student will go with the School Psychologist administering the test somewhere quiet and after some time chatting and making sure today is a good day for some hard work, they will get started. Most tests for kids start out with their most colorful and interesting subtest (a lot of them use toys and pictures) and there will be a totally different thing to do every few minutes, so I've never had a student complain they were bored (although I'm sure at least a few teenagers will insist that they totally were). The variety also means that even when a subtest is hard for a student, it's usually over pretty fast and they can feel good about their performance on the next one. For some students, I might use stickers or Gummi Bears to help motivate them to work hard, but for most, I can rely on my knowledge of cartoons and ponies to keep them engaged and make sure they do their best.
As for the tests themselves, they don't look much like other tests. Each full IQ test will be divided into about six to ten subtests. Each subtest is distinct and meant to measure a specific ability. For some, the examiner will just ask questions or (as on some tests of Short-Term Memory) say information the person taking the test has to remember. Other tests will have pictures in a book or on cards. Finally, some tests will have blocks or puzzle pieces that the student has to physically assemble. Before each of the subtests, the examiner reads some standardized instructions to the test taker. It's a skill to get good at saying these (so you don't sound like you're reading) but everyone has to hear the same thing before they take the test so that the quality of the instructions you give doesn't influence someone's performance.