I am not sure you can do everything like it is in a D&D session.
If it's an Eberron story, it should start with action. And to really shine as a D&D movie, the characters shouldn't be beginners.
The first scene is the characters having a intense fight with a group of Cultists. Maybe a classic "rescue the virgin sacrifice" scene. The Cultists are dispatched, and the group acquires some treasure, most notably an Evil Artifact. Heroes as they are, they contemplate on how to destroy it, and decide to bring it to a Temple devoted to a good deity in hope it can be destroyed there.
Obviously, the artifact will be stolen (probably the whole Temple destroyed, expect a single survivor who will join the party to fight the evil.)
Twists might be:
- The Arch Villain uses his minions to set up a false track, leading the characters to destroy one of his enemies.
- Some of the minions (or the villain itself) was actually one of the main characters allies. Probably a nice idea might be to introduce the mentor of the temple survivor in a few back plot scenes and have him turn out to be a traitor. Eberron would allow a nice twist - if he does what he does following a good diety, Detect Evil wouldn't reveal his true alignment.
This could be well combined with the first twist.
D&D Spice might be:
- Show the characters levelling up - in a subtle way.
Maybe during some of the camp fires, the groups wizard is always been seeing scribbling notes and reading some tomes, and shortly before the final attack, he stops writing down and says something like "At last, I've got it." In the final encounter, he uses the newly learned spell(s) to good benefit, maybe even surprising the villain. (Should be a strongly visible magical effect - Teleport, A Bigby's Hand, Finger of Death, Banishment, Planar Ally)
OR: Each day, they eat rations, until after on prayer in the morning, the Cleric presents them a great meal (Heroes Feast).
OR: The Rogue could have a chest they recovered from the first scene he couldn't open. But one morning, he fiddles around and it suddenly opens.
- Use D&D magic.
The temple survivor (probably a Cleric or better a Paladin) prays each morning, while the wizard studies his books. (Maybe the rogue could appear bored in that scene, or In a tough fight the group healers are disabled and the Rogue uses one of the Wands of Cure Light Wounds and heals the group. The Cleric buffs himself before aiding the Fighter in melee, the Wizard throws a Fireball (could be a scene of comic relief - placing a fireball in a group of enemies, while the Fighter is charging them - barely not inside the ball of fire.)
When interrogating an ememy, they use Zone of Truth (combined with a good Intimidate check from the Barbarian or the Rogue, or a good Diplomay check from the Paladin).
- Use D&D combat.
The fighting styles of the characters should be notably different.
The Barbarian uses mighty swings, screaming at his enemies and cleaving throw enemy hordes, the Paladin focuses on single foes and in one scene might use his mount for good effect.
Party Composition:
I think a good party composition might be Cleric, Fighter or Barbarian, Rogue, Paladin and Wizard. It shouldn't be more them them, since we want each one to shine. Barbarian has the advantage of easier adding a tracker in the group, and it serves as a better contrast to the Paladin. I think we should avoid multi classed characters, if we want it easy to spot the D&D references.
Sorcerors could be on the opposing side. A Druid might render some help to the characters (and first hide himself in a animal shape).
Leader of the Group: Either Rogue or Fighter, I think.
For twists: One of the characters is a female half orc or dwarf (Fighter? Rogue? Barbarian?)
For Eberron Style: One of the characters is a Warforged (Fighter?) or Changling (Rogue?) or Shifter (Barbarian). One of the characters should have a Dragonmark. maybe the Rogue (hiding it) or the Paladin.
For Sex Appeal: Human or Elven Female is Barbarian, Rogue or Wizard.
For Love Interest: Any of the characters is nice, but best probably Rogue and Fighter/Barbarian, especially if one of them is the leader of the group.
Combat Encounters:
- First Evil Cult Encounter
- Assault on the Temple
- Capturing Minions
- Random Wilderness Encounter (for Eberron: It should be in the Mournlands)
- Fighting a Dragon (maybe one of the enemies of the real Arch Villain) (for D&D emphasis)
- Final Encounter against the Arch Villain. (How do you beat the encounter with the Dragons? Probably by introducing Demonic or Warforged Hordes, and possibly jumping to a different plane)