It usually depends on the girl really, it is like when you see some celebrities look hot and then change the haircut and be just meh... not that nice.
I however honestly believe that if you like what you see in the mirror it will work much more, because as you leave the house you have that mindset of "I look hot" (we get it wearing suits and with a fresh haircut often) and you tell me about the results.
If you feel that you are appealing, then you will be more appealing. So you could try different things and see what you like most, only advice would be don't go too crazy, those kind of lady gaga things are not nice.
To me, most girls look sexiest with long smooth straight hair either straight down, or in a long ponytail, or straight down with eyebrow length bangs like the girl in the first link (I see this more with foreign girls), or wavy but wavy looks harder to keep from being messy and frizzy. The best color is something pure looking like light brown (sometimes seems to have golden hints which looks nice), dark brown (without random different browns), black, golden blond, bleach blond if it works on you
It depends on your ethnicity. For black girls, I like shorter cuts like Halle Berry, or dreads. For white girls l like bangs, and long straight hair. Curly hair for Latinas, long and curly. Long and straight for Asian girls.