How can i make my chain more ...hmm...tense? It seems to be too loose.

take out links.

ahh...well, if he takes out more than one or two he wont be able to get into the big-big combo.(lets not start a cross chaining arguement)

well what are your reasons for thinking its loose? I thought mine was "loose" but my LBS told me thats actually what it was supposed to feel like...so I would take it to an LBS for hands on tips before you go taking out links and causing yourself some headaches...im sure they wont charge you for an opinion

Maybe your rear der. tension spring is wore out?

Are you referring to a single or multi-speed setup?

Its a 21 speed bike. When i bunnyhop it sometimes shifts by itself, i adjusted it myself but its kind of jumpy.

It's not loose, you need to tune the rear derailleur.

Bent RD hanger?

It IS a little bent but it isnt touching the spokes, didnt thought it could be that...I guess ima take to the LBS to be sure.