Build your pantheon on the fly.
 
If a player wants to play a cleric, ask them which God the cleric favours.  Let them build the God (with your guidance).  If the party faces an evil cult, create an appropriate God for the cult to worship.  If the party wishes to visit a local church or temple, improvise.  Over time, your pantheon will evolve.
 
It's a good idea to have a list of names handy and maybe some personality traits.  But otherwise, D&D already has the mechanical building blocks available (eg, domains).  Many of the more established pantheons seemed so chaotic and mixed up because they evolved over hundreds (and thousands) of years.  You're unlikely to get that same feel by sitting down with a clean slate and trying to build something from scratch.  Also, I've found that an artificially created pantheon is less likely to get any engagement from your players.

If you want a good justification for adding gods as you see fit, go with something vaguely chaldean and give each city a patron god.  That way, you start with a few known in the area but there's an understanding that there are many more.

Quote from: Tyberious FunkBuild your pantheon on the fly.
 
If a player wants to play a cleric, ask them which God the cleric favours.  Let them build the God (with your guidance).  If the party faces an evil cult, create an appropriate God for the cult to worship.  If the party wishes to visit a local church or temple, improvise.  Over time, your pantheon will evolve.
 
It's a good idea to have a list of names handy and maybe some personality traits.  But otherwise, D&D already has the mechanical building blocks available (eg, domains).  Many of the more established pantheons seemed so chaotic and mixed up because they evolved over hundreds (and thousands) of years.  You're unlikely to get that same feel by sitting down with a clean slate and trying to build something from scratch.  Also, I've found that an artificially created pantheon is less likely to get any engagement from your players.

In the spirit of being a lazy GM, I fully support this method. Not only does it save you work, but by having other people create setting bits for your game world it makes that game world seem a bit more believeable (my own feeling on it).

As a player, I'm really big on making my own god or cult for my clerics, gives me room for that extra special touch, to realyl make the character mine.  

A belief system is a pretty fundamental thing to a person, and it's easier for me to really convey that when I really feel like I know the character's faith on an intuitive level.  

A lot of gods in real world mythologies, especially the Sumerian and Babylonian mythologies, were basically just local leaders and heros, deified and made legend with time or simply great deeds.  One leader steals the secrets to grain milling or writing from another village, and in turn becomes a legend, and in time a god, for bringing prosperity and knowledge to his people.  

I've always thought it would be sort of interesting to do a campaign where the palyers became the gods, in that sort of fashion.  You could even build off that in later games, with old PCs having become iconified as the gods of the world in time.

Quote from: PakaOn the creation of pantheons, I reckon you can't go too wrong if you just think of 'em as cosmic dysfunctional families with temples at their beck and call.  Just think of them as NPC's in any game but scale 'em up.

Now I only have to get this picture of a heavenly Dynasty out of my head.
Alexis Carrington, goddess of spite, sparkling wine, and croissants.
Thank you.

On a more serious note, the comic book  The First (the series that bound the whole ill-fated Crossgen universe together) might be an inspiration.

Give your deities HUGE character flaws - that makes them much more fun to interact with. As an example, here is the pantheon I am using in my current campaign.