The first adventure hook starts with the PCs rescuing an NPC from a beating by a couple of thugs in a dark alley. So, the adventure expects that the PCs would actually follow up when encountering that scene, as opposed to just moving on. In my case, all of the PCs were nobles from Cauldron (the city where the campaign is set) and I opened the game with all of them socializing together at the end hour of a reception of a wedding held at the Cusp of Sunrise (a noble club). After some fun roleplaying, one of the characters suggested that the PCs continue their socializing at a more casual tavern after I mentioned that the Cusp of Sunrise is closing down the reception room. That is when I started the adventure with the scene described above.
Generally, if I start a campaign I have the PCs know each other somehow, preferably with some shared history and established connections with each other. If you don't know how to start the game, just tell the players how the adventure is going to start, then inform the players that they will need to come up with a reason for why their character chooses to go along with it before the game starts.
The campaign presumes that the PCs are interested in accepting dangerous heroic missions from lawful heads of clergy or government for money that requires some investigation to succeed.
Spoliers!! (and spelling errors sorry about the spelling)
I alwasy have a hard time getting the party to introduce them selfs to the world. However Eberron is an easy setting to set some of this stuff up. Your Party has a few options
1: Suvivors from the last war: They Are comming home after 4 years of moving threw Refuge camps and the sort
2: They have been sent here to by
a: Church of the silver Flame (a good replacment for st. cuthburt. WIth gives a good reason for them looking for the Cleric NPC that you end up helping in the first encounter)
b: House **** any of the houses will do. if you have a member of the party with a Dragon mark or is tied to one of the dragond Marked houses this works well: they could be looking for a noble that has not been seen in some time (valadure or any of the nobles from the campaing) If you use Valadrure it could be a good way for the party to get to know him, he could be very helpful to the party (kinda) this would make the later suprise when it turns out Lord V is the BeHolder. Also many nobles have left Caldron so the party could be looking for a novle that left
3: ONe of my favorit ways it use Eberron to introdue a party together. is that the party (not knowing each other) is Travleing on an Air Ship\The Lighning rail\in a Caravan (any of thse will do however air ship is my favorit) and HiJackers Start taking over the ship. Trying to steal somthing in the cargo (the last laugh would work very well in this place) the Cargo should be somthing involved with the making of the Cages (money, material, somthing like that) however the PCs should loose the cargo the ship should crash... Somthing along these lines... a good way to make people who are strong who don;t know each other see that they can work well together...
4: The Church of the silver flame has sent the group here to seek out and destroy the rumers of Lycantopy in the regon finding when they arrive that there are other thing that need to be done before the Filth can be dealth with.
5: the slave traid si good too. My game (witch i finished by the way) was not set in eberron, but this would work anyway. Each Party member started the adventure With no Gear, with a bag over their head and ropes around the hands and feat. having been taking in the slave traid and the cart carring them crashed alloing them to free themselfs and stat finding out what is going on in the area.
Just some ideas