ask a guildie. though tbh if you wanna get good at arenas you really have to be playing with people who are better than and and can show you the ropes. its not really something you can learn by yourself or with other people around your skill level because you wont have anyone correcting your mistakes. You will make mistakes like overextending to get a kill, not LoSing, or LoSing your healer, using cooldowns at bad times, ect...and you wont know why you are losing because no one is correcting you.
Therein lies the problem. If you just do it "for fun" you'll lose all the time unless you learn about all the junk the previous poster just mentioned.
Just going in and doing it "for fun" and not really caring about all of that will probably get you a 25% win percentage. Focusing on learning and getting better will probably tip you over to a 75% winning percentage until you get a higher rating and you'll probably level off at 50% wins. At least that's how it was when I first started arena. I haven't done any lately so the rating system might be different (again.)
"For what is a man profited, if he shall gain the whole world, and lose his own soul? ..." - Matthew 16:26
Me and my friend used to play arenas for fun all the time... we had a 3's team with two DKs. Basically if you just want to play "for fun" find some friends, get skype and have a laugh. It was pretty awesome. We never really got past about 1800 rating but it never really mattered to us.
Timesplitters is the best game series ever! C/C The choice is clear.