Newish DM needs help

[Draconisister]

I have realized that I have no idea what I'm doing. The only reason I am DMing is our old DM crapped out on us and the rest of the group wanted ti keep playing. I have created an adventure based on A Dark and Stormy Night to force the party together. I just have no idea where ti go from there. In the end of the adventure they come a cross a Blue Psion trying to do something with a giant crystal. If the players study the crystal for a while the will see random images and fragments from the past deep with in the crystal. The Psion has a custom one time use mass cloud mind item with a really high DC so he can escape and be a BBEG to torment the party for levels to come. my world is under developed and i have no idea what to do after this adventure and I need your help o great internet gods of awesomeness also know as the Giant in the Playground Forum community.

[John Longarrow]

At low levels this is rather hard, especially without knowing what the party consists of.

In general, start with simple "Do X to get loot" adventures while tossing in some hooks for bigger plots, then see what the players get interested in. Toss in social items that won't happen for a few months (fairs, tournaments, contests, local nobles daughter/son hitting age of adulthood-needs to get married). Mostly you get to toss out a bunch of hair brain ideas and see what sticks.

Town is suffering a plague that can't be cured (demons doing something)
Town being attacked by undead (evil cleric behind it)
Raiders hitting towns along the coast. Bounty on leaders head.
Goblins attacking travelers along a road.
Evil Fey in a forest to the north.
Werewolf attacking village in the area.
Bounty on evil guy.
People are disappearing near old ruins.

Toss things out. Add in a guild of bards that work as an adventure job board. Have a group of mighty hero's the party can hear about. Tell stories of old wickedness in the mountains.

At low level, most of what you toss out will sound too powerful. Some of it, how ever, will stay in the parties minds as something to work for.

[lytokk]

I would say leave it open to them. Put the idea in their head that the BBEG is going to be around for a while, and maybe they should research some way to defeat him. Depending on how much world building you want to do, you can have the answers being in another town, where they have to travel. On the way there, they have some adventures, running into a group of goblins who just attacked a caravan, following them back to their warrens.
Having a travelling party is great for world building, since you can build at the pace of the party's exploration.
Try to leave it open to the players to decide what you want to do, but I'd recommend building a few different dungeon crawls and being able to populate them on the fly. So if the party decides to enter a dungeon, you've got the map right in front of you already made, just needs to have some creatures put into it. Try to plan for as many different paths as possible, and don't feel bad if your players don't use all of them at first. You can always repurpose the situations by upping the encounter level if they've gone up a few.