Maybe I'm just a bit mislead, but what level were the characters going up against the flesh golem? Was it mere bad luck that brought them down or were they simply outmatched? Seems to me like it might have been the latter. One way to avoid outmatching your players is to make copies of their character sheets and, in your spare time, do a "sparring match" against the creatures you have in mind. If you suddenly realize, "Hey, no one here has a weapon that can even hurt this thing and there's no other way around it..." well, you've just saved everyone a great deal of time.
As for storylines, plotlines, etc. search out novels, movies, or the endless number of resources online. If you're really stumped for ideas look through the Adventures section of
www.wizards.com/dnd for one that seems to suit your interests and needs. Try to find ways to incorporate each character into the adventure and use it to bring them together. If you find the right adventure and have the right connections between the characters you should be able to give them reasons to stay together.
I recently ran a game with two rangers and used a WotC adventure to bring them together. One, a gnome ranger tracking a kobold chieftain and his bodyguards who managed to elude him...tracked them right into the hills where the elven ranger was travelling. The elf was on his way to visit a dwarven alchemist, looking for a cure to a strange sickness afflicting his village. The kobolds are dispatched, and the two rangers share their stories. The elf discovers that the gnome was once the dwarf's errand boy, fetching various herbs and ingredients for his potion. This was before the gnome's entire family and home was razed by kobolds. Basically, the elf realizes that he is more likely to get the dwarf's help if the gnome goes along with him. The gnome, having gotten the last of the kobolds he was after has no other immediate direction, and agrees to help.
So, try a pre-made adventure and see if it generates any ideas on where to go next. Use the character's backgrounds if possible. I always flesh out the characters by asking them questions before we begin play. Questions about their families, their loyalties, their ideas on religion, their prejudices...it provides plethora of possible plot elements. And, if none of this works, just find another pre-made adventure that works...and go with that. Eventually, hopefully...the creative juices will return in time.