I both agree and disagree with what's been said so far, but my agreement and disagreement generally hinge on what kind of story approach you're going for.
If you're just wanting to do an indefinitely ongoing comic with some characters you like, then just come up with a cast of characters, a setting where they can do their thing, and a unifying premise that lends itself well to repeated cycles. These aren't very hard, in my experience; naturally, the characters will need goals, as well as motivation to reach those goals. They will need some antagonist or problem. Just come up with a theme for the episode or chapter and go with it. With practice, you'll soon not only have the characters down, but you'll also be able to start coming up with little things that you can indicate and then develop later. This can be foreshadowing or not, it's up to you. This is a formula that has worked for ages.
Make sure it's a premise you like. To that end, develop it over a period of at least a week or two, to be sure you'll have the requisite dedication to it. If after, say, a week you're bored of it...you probably won't be able to do an ongoing comic based around it. Enthusiasm is usually ephemeral, but if you can maintain some level of interest at least, it can be a good experience that is viable.
The other approach to a comic is to just come up with a story that has a distinct beginning, middle, and end (as opposed to the cyclical/episodic approach), which can be either better or worse, depending on how it's realized. In my experience, these tend to be shorter, which may be ideal for a first foray into comics. Maybe you should do a short story along these lines and see if you enjoy it.
Ultimately, doing what you want to do most is probably going to be your best bet, especially for a first try at comics. Make sure you have the continued interest in it by making yourself take the time to develop it and work on it. But have fun! 