Disclaimer: I am new to DrunkDuck, but I have been planning stories for quite a few years now. I always tended to work with an artist, so most of my work was in the planning stages in helping with storylines. This guide is about sorting out your ideas, both for characters and plot. This is just a base for sorting out ideas, it's best to develop your own style. :)

Notes before you start

Always, always, always keep a notebook or sketch pad with you. You may come up with a random idea and want to jot it down. If you have no immediate access to a paper and pen, pull out a cell phone, or other electronic and find a place to save it on that.
Also, when you get in a comic/story writing mood, focus on it, and think about it all the time when you aren't with people. If you have friends who will listen, bounce some ideas off them.

I. Character Development
Physical Features
Past
Personality
Comparison to Others
II. Plot
Start at the Beginning
Start at the Middle
Start at the End
III. The World
History/Creation
Physical Appearance
Natural Laws
IV. Take notes


1. Character Development

There are several places to start.

Physical Features

The easiest, in my opinion, is what your character looks like. A good way to go about this is think of things you like. Favorite hair color? Eye color? Skin tone? It's best to only use one feature as a starting point. I tend to make a lot of red headed characters, as I think red hair is very pretty. Picking their nationality is also a great way to start, as it leads straight into how they are physically built. If you have an Asian character, you know they will have darker hair and eyes. If you know what kind of clothes you want your character to wear, base their looks around that.

Past

Instead of working on the character directly, look a bit into their past. What did they do through before the story started? This may shape what they do for the comic, and explain why. Ex. X character grew up with a silver spoon in their mouth. After a band of raiders came and destroyed their parent's home, X had to travel by his/herself. He/She now has problems coping with having to deal with the poorer side of life, like sleeping on the hard ground, and not always getting a filling meal.

Personality

The personality of a character can start out very simple. When you start with ideas for the personality, you can start with “Happy” “Mean” “Cynical” etc. Try and find a single word to describe them. This lets you have a base point to then expand the character. Maybe their happy with a darker side, or mean in a good way (ex. X tends to push people a lot, but it's later reveled, it was because something was always coming towards the people) Depending on style, this may also shape what the characters look like. In Anime, as an example, happy-go-lucky characters have larger eyes and more cute-ish features, while serious characters are much more angled looking.

Comparison to others

Another great starting point - mainly for secondary/tertiary characters - is how you want them to compare to the main character(s). If you want them to be the opposite of your character, then start listing your main character's traits, and find the opposite of that. If you want them to look up to the main character, come up with little bits of their looks or personality that is like the character they look up to, but a bit more immature. If they are a role model for your character, try to do the same, but make the little bits more serious.



II. Plot

Start at the Beginning

When you try to work on your plot, jot down ideas that would help introduce your characters. Is there some big even that will start the plotline? Is there an important thing happening for one of your characters? Maybe you need to make a start to the story by explaining a bit of background of the world your readers are in! (For comics, this probably shouldn't go past a page in the webcomic)

Start at the Middle

You can come up with a big action, or substory, that happens in the middle of your story, and build from there. An example from this is the start of the Twilight series. Stephine Meyer came up with the meadow scene in her first book before knowing even the characters' names. Maybe you know a big fight that will happen between your characters, or some event you know will take place in the story, and can use the information from that to foreshadow things in the beginning, and reference back to it in the end.

Start at the End

Sometimes knowing where you want to end up is the best way to start a story. If you have a final destination in mind, it gives you a chance to have the events foreshadowed in your story. Perhaps an insignificant name in one story will turn out to be the main plot of another. ((Ex. Sirius Black is mentioned in Harry Potter and the Sorcerer's Stone, first chapter. In Book Three, Sirius becomes the “main antagonist” for most of the story.))

III. The World

History/Creation

Sometimes you could start with what you want the world to be like for your characters. In one story that I have self-published, I created the entire history of how the world of was formed in my story. This gave me a very good base for figuring out what each of my characters believed. While you don't have to do an entire “Creation Myth” for your story, sometimes it's good to make a new world, with different surrounding ideas for the residents.

Physical Appearance

In the world for characters, sometimes you should sketch a map of what they are walking through. Maybe you made a continent like North America where there are a lot of types of land - mountains, plains, valleys - or maybe it's closer to China, where there's only really one type of land - China is mostly mountains. This can greatly influence what the people of your world will be like.

Natural Laws (Last one!)

Another great way to start, is maybe you need to change the natural laws of your world. Instead of the air getting thinner the higher you go, maybe it gets thicker. Heat may stay on the ground instead of rise above the cooler air. If you do change the laws, try and come up with a reason why. In a story I have, instead of the sun being a giant star, and the moon being a giant rock that reflects the sun's light, I made them eyes from a dragon. The moon can still close it's eyelid, and the sun was pushed when it was first put in the sky, which keeps it slowly circling the world it looks down at.


IV. Take notes

Plain and simple! When you start coming up with an idea, take out a piece of paper or a notebook and just write down what comes to your mind. It doesn't even have to be neat. Just write down what you think. If you come up with a idea that goes with another one, write it down and make a link to the other one (an arrow, circling them, etc). When you go researching for parts of your story, jot down what you find under a title, like “Words for ”
And if your ideas keep you up at night, take a moment to do a sleepy-written scribble on your notebook before trying to sleep again!

… Hope something here helps!