When I choose an anime for watching, then I watch all episodes of it; how it is fun or not(Oh, there is an exception; Re: Cutie Honey). Because it is not so comfortable for me to stop watching with unended story. Therefore, I carefully choose an anime to watch.
First of all, It is the easest way that there is next season of an anime and I watched earlier season. If the earlier one is not so bad, I make my mind to watch next one. For this reason, I choose Tsubasa Chronicle 2nd, School Rumble 2nd, Galaxy Angel Rune, Mai-Otome, and Black Lagoon the Second Barrage. I will also watch Zero no Tsukaima 2nd.
For the second, if the background of anime is something special, I get interest of it and watch it. For examples: Fullmetal Alchemist, Death Note and Shingetsutan Tsukihime; I will watch Denno coil.
If the original platform is a novel, I get some interest. By this rule, I chose Suzumiya Haruhi no Yuutsu and Zero no Tsukaima. The result is awesome! Very good.
If the animation is related to Japanese manga/anime curture, I get interest about it. By this way I chose Gensiken, Comic Party and Welcome to the N.H.K(but Welcome to the N.H.K is not so). Now I have interest in Doujin Work.