When I went to type the title of this post, I misspelled both words. Conscious and conscience are both hard to spell all the time, and that's not even their biggest problem. They sound alike and they have similar meanings -- but they're different enough to make it a terrible writing faux pas if you put one where the other ought to be. There are a few tricks to keeping them straight, so you don't have to pull up reference material every time you want to use one or the other.
The word conscious can be used in a lot of ways, which only adds fuel to the fire of writing confusion. In the main, it really means aware. You can be conscious of the fact that you're reading a blog, you can be conscious of your surroundings, you can feel conscious guilt.
But you also have a conscience.
It's that inner voice that tells you something is wrong. When you feel bad about something you've done, it's your conscience making you feel bad. It causes guilt, and regret, and all those other feelings. That's the main thing you need to remember about conscience -- it creates feelings. Conscious, by contrast, is awareness.
To make matters even more confusing, the word conscientiousness exists. Clearly an extension of conscience, it means something like listening to your conscience. It's usually used when someone is doing something with great care: She wrote her blog posts with conscientiousness.
Sorting Them Out
Conscious and suspicious both end with the same suffix, and if you break them down to basic meaning they are closely related. To be suspicious is to be especially aware of someone's questionable behavior, yes? You have to be awake and aware to be in that mindset. I use tricks like this to link certain words in my mind; then, I can remember that you have to be awake to be conscious.
Your conscience can keep you awake at night. It's got the word science in it, and naturally this makes one think of crickets. This leads naturally into Jiminy Cricket, who is (wait for it) a conscience for Pinocchio!
Really that's not a very easy trick even if you are very familiar with the story. Here's a better one: science is the opposite of feeling (since feelings can't really be gauged on a machine), so add con to science and you have conscience, feeling. Conscience is also longer than conscious, letter-wise, so you can always try to remember that the longer words go together. Conscience = feeling, conscious = awake, long long, short short.
It's easy to mix up even the simplest words, and I do it all the time. Every writer does, because the fingers are often faster than the brain. You're going to make mistakes when you write, so don't worry about that. Always go back over your work, and catch all the errors in the editing. Don't stop yourself while you're writing to worry over grammar problems, because you should be making mistakes when you write. Sometimes, mistakes actually help you create something even better. But if you don't go back and edit, I won't feel sorry when your conscience bothers you!