This advise is coming from a professional aquarist. I breed and raise fish for a living, including over 3,000 betta's.
First of all forget everything that you have been told about bettas, from reading the previous posts its all wrong.
1) Bettas need at least 2.5 gallons to be healthy and happy. Sure you can survive in a tiny little 8x8 box but would you be healthy and happy?
2) Bettas need weekly water changes, aim for 25 to 40% for those kept in 2.5 + gallons. Anything less than that and they need 100% every other day at least.
3)Bettas kept in small tanks suffer and die from ammonia burns, and diseases such as fin rot, ick, etc...
4) Make sure to have some hiding places. Bettas are smart and like to have plants, rocks, caves, etc.. to swim around and in. They are some of the smartest fish you will ever have.
5) feed them 6 days a week and always fast them for 1 day a week to avoid constipation, which is deadly for bettas if not taken care of right away.
6) Bettas as all fish DO NEED FILTERS!!! They need clean water just as you and I need clean air.
7)In the natural, bettas do not live in puddles, they live in rice paddies, HUGE DIFFERENCE!
Plight of the Betta
8)Bettas like company too! There are many many fish that you can keep with your bettas. I have bettas in 3 of my community tanks.
9)Mix up your food choices. Would you like to eat pasta every day of your life? Some favorite foods are frozen bloodworms, live worms, freeze dried food, and even veggies!
10)Its fun to see them flare, but making them flare too much and too often can stress them out which makes it much easier for them to get sick.
Those are the basics. :) Let me know if you have any questions and I'll go reread the posts and see if anything else needs correcting.
Hope this helps :)