What not to do when playing D&D

I've recently begun playing D&D (dungeons and dragons for the uninitiated). It's a roll playing game where you create a character with certain attributes and go on adventures and deal with any problems (usually monsters) the dungeon master throws at you.

Since I'm new at this I've compiled a list of mistakes I'm trying to learn from. So here is what not to do based on my own experience.

#1: Don't let someone else roll (create) your character. My friend James rolled the stats for my character while I picked out other stuff. And that is how I ended up with a -1 dexterity and a -1 initiative. Initiative isn't that big a deal but with a -1 dex I can't dodge anything or be stealthy at all. The heavy armor I'm wearing doesn't help either but that's besides the point.

#2: Don't let someone else choose your spells. James also chose my prepared spells (I'm playing a cleric), and gave me one where I could make the ground shake and thunder but it doesn't actually do anything. Why? Why would anyone choose that?

#3: Team shit show. We have some team members who make very questionable decisions. At every turn. Add that to the fact that half our party keeps rolling super low and you get what we've started calling team shit show.

Basically we end up going in with no plan, and just attack, but we're not that skilled so we end up all almost dead and running away as fast as possible.

#4 You don't need to interact with every NPC you meet.
We spent like 3 hours on a caravan trying to get stuff to happen when we met people but they refused. After the first hour, just leave them alone until you get to your destination. Maybe then it wouldn't take 3 hours.