It's kinda ridiculous how it's the end all be all for if a movie is good or not, when it's really just kids who spent 7 hours a day on the web. Of course everyone is a movie expert now. Do I really need to read 20 reviews before I see if I should watch Nick of Time ?
To me RT is just a bunch of hipsters. In fact I actually saw one critic on there give Lion King a bad review because he said the Elton John songs weren't hip enough
Also when you have a 50 year old white woman reviewing Barbershop or Next Friday or something, you're not gonna get an accurate interpretation of it because the movie's not aimed at her. I can tell what movies are gonna be horrible, which ones will be stupid funny, which will be a more clever brand of humor, and which ones have good potential to be something special. I don't need "professional movie watchers" to tell me that.
First, to be one of the critics that count for the main score, you need to have your reviews published routinely (there is some credential that you must meet, it is explained somewhere on the site).
Then there are a few things one should look at when determining certain things. First, most people look at the %. However, that can be misleading if you overlook the average score. Some movies will have an 85% approval rating, and people interpret that as a great movie, but the average rating may only be 6.4/10, meaning that 85% of the critics thought the movie was slightly better than average. Even more important than those scores IMO, is the quotes from different reviews. If you know what you like in a movie, the quotes (which generally are good at avoiding spoilers) give you some idea of strengths and weaknesses, and you can compare those to what you like in movies. I've seen reviews for movies with 25% approval ratings, which sounds like a terrible movie, but then I will see that many of the critics hated the over the top violence of said movie. I personally like over the top violence in my movies, so that sometimes is an indication that I may like the movie more than the average critic.
If it's extremely in one direction or the other then you have a pretty good idea of the quality of the movie. Movie critics don;t agree to that degree often.
If it's in the middle then you just have to take a leap.
I often only check it after I've watched a movie. To see if my personal thoughts had been echoed by others. Sometimes I disagree whole heartedly (Ping Pong Playa in particular), but for the most part I find them to be spot on.
But it's just a collection of professional reviews, you can assign importance to whomever you want on the site. It's a nice site.
For those that say IMDB is better, what is it that they offer that RT doesn't? Do you trust the people who rate the movies more? I like how RT has critic and fan reviews, while IMDB only has fan reviews, correct? Is it that you side with the users of IMDB more? I use IMDB more for movie information and casts, etc, while I use RT for the reviews.
In the end, I think the better one depends on which is easier for a give person to interpret and predict how well they'll like a movie.
And for those who say that a trailer is all they need, sometimes trailers are misleading. The Watch is a current movie that I thought looked good, and I expected a rating in the 70% range. After reading the RT reviews, it sounds like crap and I'm going to save my money. I'll still see it eventually, and I could still be pleasantly surprised, but I'd much rather save my money and give it a chance later rather than regretting spending $10 on a movie that is potentially a huge waste of time.