To rant well one must follow heavily influenced, regimented guidelines.
1) Think of something that annoys you more than anything. It doesn't have to be something big like world hunger, it just has to be something that you really really really don't like.
2) Make sure you know a few things about what you're going to say. It might hurt not to just blow thinking of that angry thought, but think before you speak. If you don't really know anything, or have any experience dealing with the thing that makes you angry you will just end up looking like a fool. Like I might think that foolishly abiding by the trans-capitalist policies of the Chinese foreign markets is going to hurt our economy and depreciate the value of the average consumer's spare change, but other than that heavily worder sentence I don't know much else about the topic. If you don't know anything go back to step one and start again.
3) Start off slow. If you jump right into the rant and just give in to your brewing anger than you will just end up babbling like a crazed loony. By starting off slow you can introduce your audience to what you are mad about and begin to list the faults or terrible traits of that thing you wanna talk about. It also lets you escalate without making people uncomfortable.
4) Don't yell. Yelling instantly increases the tension of your audience and can only hurt the point you are trying to get across. In the case of writing a rant or typing one ALL CAPS WILL ONLY MAKE PEOPLE ANNOYED AND UNCOMFORTABLE, GOT IT?!? See? That was just annoying.
5) Bring in personal experience and humor. By bringing in your personal experience you can relate to your audience and make them think you are just a down to Earth guy that is just a tiny bit ticked off. Using such experiences helps illustrate your point and will be worth your effort, unless of course you choose an off topic story in which case you missed the point completely.
6) Tie everything together and make your point. A rant without a conclusion is like a wedding without a cake. By tieing everything together you will be able to illustrate your point while proving that you aren't just some angry idiot. Hopefully if you illustrate your point well enough you will also sway people into thinking the way you do and make lots of friends with an appropriate rant.