#1
Originally I planed to buy an ordinary 6 string acoustic guitar, but now I saw that 12 string on ebay. It?s just about $ 120, so I really consider buying that one, as I heard that the sound of a 12 string is much better. But the problem is that I don?t really know how to play it. How do you use these extra stings??

Hope you can tell me something about it!
#2
well you can do some crazy 12 string stuff like nile does, or for chords, just take 2 strings per same note, like if you playing a power chord, do it with 4 strings, not 2
#4
12 sting can sound better - most noticably fuller sound, but as John Butler and company and they will tell you that it's hell on your fingers and nails - especially if you enjoy fingerpicking. Can also be tough on your left hand (assuming you're a right-handed player), especially bare-chords higher up the neck. But essentially, you pay it like a regular 6-string. Cheers
#5
essentially if you grabbed a six string guitar that was an octave up then normal and then paired the strings up with the normal strings and you would have a 12 string guitar

6 string tuning
EADGBE

12 String tuning
EeAaDdGgBbEe
Gear:
Washburn RB2500 (5 String)
Yamaha BB400 Fretless (1981)
Carlo Giordano 3/4 Upright (White)
Cort Action 4 (Stereo-fied)
Orange Bass Terror 500
Orange 1x15 Cab
Boss GT-6 Bass Multi-effects