Bring ear plugs. Seriously, if you value your hearing!! Right up in front of the stage is fun and cool and all, but I've got excellent hearing and want to keep it!! Don't be the fuct up guy hanging in front of the speaker stacks!! I'll send you ear plugs in the mail if you want!
Depending on the venue and the crowd, there can be a lot of security and they'll frisk everyone...most likely at the one you're going to they will. Some concerts I've gone to they look through everything, check your hat for drugs, etc.
I recommend hiding a joint in your shoe, and staying away from the mosh pit. Keep your guard up, some weird people are at concerts sometime. Most people are mad chill, having a great time just like you...but there are always the few bad apples.
Back when I was your age or younger my friend passed out at a Pantera concert after taking a hit off of a pipe someone passed around. No idea what was in it....probably not just weed. Bring your own, and don't get caught!