Everyone plays differently. The first run through, I did the full melee Jedi, so I usually had Carth and either Mission or Jolee. Bastilla too, but I liked Jolee better in terms of what he can do. He's also the cranky old man Jedi and that's just awesome. (Make sure you keep talking to him so he'll tell you stories. I laughed so hard at some of them!) Anyhoo, it's always good to have at least one blaster in the party, and if you keep Carth leveled up and give him the best blasters, he's going to be the best at it. Mission does pretty good with blasters, and she's near essential if you're not going to level up demolition or slicing, but she's pretty weak and can go down quickly if you're not careful. Now, I actually prefered to go through as a blaster Jedi. I thought it was a lot more challenging, and then my party had to include either Bastilla or Juhani for melee. Really, just think about your fighting style and make sure you have at least one melee and one blaster in the party. And SOMEONE that can heal, either it's you or one of the other Jedi. Seriously, that will make things easier in some of the tougher fights! As for grenades, I only used them in a few spots. Mostly, if I was in a fight that was really tough and I had to restart it, when the fight started, I would pause and fill everyone's bar with grenades, and the procede as normal. Lobbing 12 grenades at the baddie right of the bat can be helpful! I didn't really use traps, either, except at the end which would be a spoiler so if you get there and want to know about it, I'll tell you. I really didn't micromange hardly at all. Setting a behaivor type for each member is really all you need to do. The AI isn't always the best, but most of the time it's good enough you shouldn't have to micromanage them. Keep an eye on their health, because they kinda suck at watching their own health, but a quick character change to heal them is all that's needed.
For Force powers, even if I was light side, I still took all the Force Lightening tree powers. That's probally the most useful offensive power in the game (at least, IMO). Plus, running down a hallway spawning Lightening Storm and killing everything in my path just makes me giggle like a schoolgirl. But pick what you want now, because you can't level past 20.
And when you've finished it, there are some pretty good mods out there you can download, including a few story mods. It's not as extensive a community as Oblivion or Skyrim, but there are some good stuff out there. Makes multiple play-throughs more interesting to me.