I'm weak at building characters.
What resources are there to create rich characters? I'm thinking beyond name generators: Quirks, biography, diseases like allergies, hobbies and jobs, wealth, omens, ...
I was taught to do character writing exercises.
The biggest questions you need to answer about your characters are along the lines of the following:
Basically you need to find the motivations for your characters' actions.
Beyond that your biography should fit naturally with the motivation. If your character fears technology will ultimately render humans useless, how interesting would it be to have him pulled into a tech support role at work unwillingly? If your protagonist has an omnipresent fear of death, a serious allergy to peanuts would provide a great tension in the story.
Well, J. Michael Straczynski said he had three basic questions to help build the core of a character. They also provide something from which to build interpersonal conflict.
As for the rest of the character, there's always the issues of what they like to do when they aren't in the story. Hobbies and interests, but is it worth mentioning if it doesn't come into play with the story at hand? Then again, you should always know more about your character than your readers do, it helps make them feel fleshed out.
Sometimes it can be helpful to use your plot to extrapolate what the characters who are involved in it are like. Let's say you're writing a story about a long sea voyage. Right away, that tells you that the main character has some sort of reason for being on a sea voyage. And once you know what that is, you'll know a few things about who this character is. If your character is going out to explore the world, that's going to indicate certain things about his or her personality (adventurous) and possibly the resources he or she has access to (the money and supplies needed to mount such an expedition, including the ship). Then you can go a little deeper into why this character is looking to explore the world, which will suggest still more about the character. Is this a grizzled veteran sailor looking for one last chance to discover something and gain a place in history? Or perhaps a naive noble who thinks going to sea will be a fun adventure? Or maybe a sailor hoping to strike it rich and make a better life for his or her family back home? That's only a few of the possibilties, but you can see how each reason for wanting to explore at sea would suggest a different background, social status, and personality for each of these characters.
Of course, just deducing character traits from the plot can lead to boring, stereotypical characters. So once you have the basics, play around with it a bit. Ask yourself "What would happen if this person was A instead of B?" Doing that a couple of times and picking the results that lead to the most interesting character while still giving him or her a reason and capability to do what your plot requires.
As a couple of other people have already said, don't add quirks just to add quirks. You will probably want to figure out the particular ways your character show certain emotions or what he or she does when there's not much else to do. But there should be a reason that makes sense in the story for everything that happens. The fact that your character is a terrible trumpet player isn't important unless your character has a plausible reason to play the trumpet or talk about playing the trumpet during the course of the story. The character's lack of trumpet playing skills may reveal how she has never really finished anything she started before or how he had a bad relationship with his father, but you still need a logical reason for it to come up in conversation or for the character to play the trumpet, let alone bring it on a sea voyage.
I highly recommend Orson Scott Card's Characters and Viewpoint. It's an excellent book (probably the best book on writing that I've read), and he discusses a lot of important issues in building characters that are very insightful.
Not only shopping lists of details, but how the character is viewed by others; their past; their motivations. He talks about how you can choose characteristics, traits, and quirks that dovetail well with the character's role in the story, and how to portray those elements and make them significant.
Beyond that, the details you mentioned are all good directions - and any one idea can be the germ of a great character. Actively look for interesting ideas you haven't seen much, or even commonplace ideas you haven't seen much and why they might be interesting after all. For example, one author I read wrote a story about a high-school band master; I'd never read a story about someone of that profession before, and he did really neat things with it - and got a lot of compliments from band masters who were thrilled to see a great story about one of their own :)
One thing you could try is looking at the Player Hand Books (PHBs) of some paper Role Playing Games like Dungeons and Dragons or Palladium. Some of these have tables that you are able to roll various dice against to get a random character. You can find games like these for almost any genre, but it really doesn't take much to modify from the fantasy books. Palladium has several tables based on character flaws, addictions, phobias, etc. if I remember correctly.
You can even use the tables as examples and substitute more applicable traits into your own tables.
There may even be online applications for these games (created by players) to automate character generation.
I have found character sheets for online roleplayers in MMOs to be very helpful for fleshing out characters; after all, the main thing that their writing is based off of is their character and the world.
Obviously some points have been added to the character sheets to accomodate the peculiarities of the fantasy/game world, but they're easy enough to delete/change when copying the sheet over into Word/Open Office.
Forcing myself to fill these out--and fill them out extensively--has always been very helpful for me to invent a well-rounded character whom I know well.
Obviously a lot of this has to come from your own creativity, too. It wouldn't necessarily occur to me to list "narcolepsy" under random quirks without a lot of practice in thinking outside of the box.
Unfortunately, I can only post two links because of my current reputation, so I had to cherry-pick out of the many different resources for roleplayers (and therefore character-building) I found.
At the end of the day, loves, hates, motivations, and a distinct voice and "feel" will make your character stand out to the reader, and I assume that's what you're going for. These are just tools to maybe help you figure that out.
My answer to that question pretty much gives a way of analysing characters by cross referencing simple archetypes with the Enneagram of Personality.
justkt's answer pretty much covers my thoughts. Here's something that may not be obvious (took me a long time to figure it out at least): develop the character as fully as you can, but don't feel compelled to demonstrate every facet of the character that you decide upon, or to elaborate in the story on every little trait. My earlier writings, as well as those of a lot of my peers, would be a futile exercise in trying to stuff as much of my predetermined character build as opposed to using that build as an outline to determine their actions (as justkt said).
I personally don't feel that compiling laundry lists of attributes helps to develop characters. The most important thing you need to know if the character's function in the story. Hero's best friend? Assistant murderer? Beyond that, each character needs a personality. Think of your friends - you may not know what kind of ice cream they like, or what their favorite book is, but you know how they act, and how they talk.
Is the character timid or outgoing? Serious or silly? Do they tend to go on a bit, or are they more laconic?
My own advice is to shamelessly steal personality traits from people who you know.
I wrote a short story whose two characters were a white-collar criminal being held under house arrest in rural Maine, and a guerrilla soldier who broke into her house. It became clear as I developed the story that these characters had different value systems: the soldier saw himself as a warrior with honor and pride, and the criminal saw herself as a rational businesswoman. On the one hand, I really liked the dynamic that this contrast gave to the story. On the other hand, I haven’t sold it yet. :-/