Going to my first concert?

This april, a friend and I are going to a Blue October concert. I've never been to a concert before, so I'm a little nervous. How much can you move around the concert area? The ticket I have is general admission. How does one behave at a concert for a band like Blue October? Is there a lot of movement and yelling and noise, or not so much? Is there behavior that would be considered bad? Also, how early should I try to get there, or if the concert starts at 7, should I just get there at 7? And how long do concerts usually last? Are there certain clothes I should or should not wear? People I should be wary of? Is a purse a good or bad idea? I'm sorry I have so many questions, I am just really nervous! Any advice is helpful :)