Tales of Symphonia

Where are you at in disc 1?
Sylverant or Tethe-alla?
and who are the charaters you are with (their are 8 total, 9 if you count Kratos and Zelos)

As Relm98 said all melee-- however, if you feel confident, you won't neccessarily have to bring Raine along. Zelos and Regal have healing abilities, and Sheena has purgatory seal, so you could conceivably go the entire game with all melee fighters.

The best assault team is probably Lloyd, Zelos/Kratos, Sheena and Regal. They are all monsters in attack, but Regal has a really bad defense. If you don't want Regal die too soon, give him the don't pursue command.

The best party for me was Lloyd,Genis,Raine,Kratos/Zelos. While they may not be able to do as much as attacking as the others think of it this way: Lloyd and Kratos/Zelos will pummel the enemy,Genis will devastate them with long range magic attacks,and Raine will either join in with Genis or heal your team which means you dont have to pause and use gels constantly especially in long ass fight. But of course if that's not your style i'd go with Lloyd, Kratos/Zelos,Presea,and Regal.

For pure attack? Lloyd, Genis, Zelos/Kratos, and probably Presea.
Sheena's attack is too low, and regal is an awkward fighter.

Personally if you want to deal some big damage, I stick with Genis myself as well as Lloyd, Regal and Presea. You don't need Raine really after your first Visit to Tethe-alla anyways. I don't use the Magic knights(Zelos/Kratos) cause they spend more time casting than fighting and it becomes pointless at higher levels where even presea is doing much more damage. The real question is which training method are you going to use for each character? Genis has really good spells on both sides. As for the others, it's really up to how you want your characters to evolve in battle. But Regal's grand healer will help later on.

What I normally do for battles is:
Presea
Genis
Raine
Zelos/Kratos
While I play Genis, Raine heals and the other two are on the frontlines. You can easily swap Presea with Lloyd, if you don't have her yet. But she packs quite a punch. Also, Colette is good, but I rarely use her. I don't use Regal except in a few instances. My way has gotten me through more than twenty games, without dying once... But ultimately, it is your choice.

This question is a matter of opinion. If you want raw power, I think I've broken it down to where Colette, Presea, Regal, and Lloyd deal out the most damage, not exactly in that order. Colette's a beast if you spell cancel combo, which will lock down most enemies with ease.

I picked this order to me it's a good balance, Lloyd, Kratos, Sheena, and Raine, if you don't have Kratos then use Genis, I completely hate having Zelos in my group.