It depends on what aspect of the film you're criticizing.

Emotion, entertainment value, parallels with other films, the work as a whole; you can do that with out any filmmaking experience.

But if you're judging how the film was made, the acting, writing, directing you need to be in the arena. You need to know what a person in one of those roles could actually influence in the final film.

One of the other comments here says anyone can tell you if food tastes good and that's true. But you better have more cooking experience than watching the Food Network if you start talking about knife technique and oven temperatures.

I think I would go with something like Stephen says. I'm thinking close up / detail shots where things are slightly different and you cut through them quickly as the action happens. A hand putting a dish in the sink, and every 12 frames she has on a different shirt. A plate of food that repeats the same 3-4 meals for a few seconds. At the woodpile, film it over several days so you get slightly different light.

Stephen's advice is great if you're looking to make this your career.
Jofre has good advice if you want to try it out first or do it as a hobby.

My advice is to see what kind of journalism courses are in your school. Most schools with a journalism program will have a course on video production. Yes it will be news/documentary focused but for someone with no experience it will go over basics like like how to use a camera, how to edit, how to tell a coherent story, etc. If there isn't a class stop by the school paper and see if they're doing any video.

Lastly some schools use strange terms when talking about their video/film/movie courses. My local school calls it's program Visual Communications or ViCom, other colleges may call it Mass Communications.

There are so many variables. Do you need to move everything yourself? Do you have access to a vehicle? Do you often go places where vehicles can't?

I have my camera and lenses in a Pelican 1510 with TrekPak dividers. My camera cost me more than my car I want to be sure it's safe. I know it's safe inside a Pelican.

Other stuff (audio, computer, other accessories) I keep in a Lowepro backpack. I plan to switch to a Cinebag CB-01 so I can fit more. I have a RocknRoller RMH1 Multi-Cart Mini-Handtruck arriving on Thursday, the plan is to put the Cinebag, Pelican, stands, tripods, etc on that so I only have to make one trip from the car.

Also don't expect one solution to fit every occasion. If I want to go super light I have another Lowepro bag that will fit camera, one lens, audio recorder, mic, and headphones, and I can strap a lightweight tripod to the outside.

Get permission. Guerrilla filmmaking is about being quick, using the real world that you find, not creating sets and spending 10 hours in one spot.

Best case scenario the police will kick out out before you're finished filming. Worst case scenario is getting arrested while kicking you out and being charged with littering, filming without a permit, trespassing, or disturbing the peace.

Actually no, it's a gang war drama, does that mean you'll have weapons? Worst case is one of you gets shot because the police don't know your weapons aren't real.

Get permission.

School newspaper. You may not necessarily be interested in journalism, but journalists are storytellers just like filmmakers. Most journalists love writing, they'll make the story you just have to translate it visually. It may not be the most exciting work, especially in high school, but it will give you experience working the camera and editing.

Oh, and the first stuff you make is going to be horrible. The first stuff anyone makes is horrible. You're going to make mistakes. It's much better to make them now in high school.