There are tons of options available to you when it comes to editing your audio and everyone has their own workflow based on their experiences over time and what's worked best for them. This was my personal workflow up until last summer when I got a mic I could use with ProTools. I used this workflow to record for a number of games, including Heroes of Newerth and Deus Ex: The Fall, so it's definitely a matter of how you use your tools and not necessarily what you have.
Here are some basic tips and techniques that you would use pretty regularly to edit your audio.
If you've ever used a computer, the concept of cutting or deleting text, objects, or images, is fairly universal. Audio works the same way in a DAW - allowing you to select portions of your audio (represented visually as wave forms) that you may not want to use (such as silence, your body making weird sounds, or your family walking in to ask you why you're making so many obnoxious noises) and then delete them. Like text, you use a cursor to highlight the section of audio that you don't want, either after listening back to preview it or by designating obvious silences or unwanted sections by sight, and then you're able to use Control (or Command)/X or Delete to remove those sections out of your track.
Cutting and deleting will easily be 80-90% of what is involved in dialogue editing no matter what experience level you're at.
Leveling is a term that comes up around dialogue or voice editing a lot. Mostly this involves making sure that your audio is at a consistent and strong volume level from start to finish. Usually, this is good to address after you're done cutting out extraneous sound and all you're left with is the audio you plan to send clients or work with yourself.
As an example, we can look at the image above (the After picture of the Cut/Delete section) and see that some parts of the audio wave forms are smaller and shorter than the others. The smaller and shorter they are, the softer they will be and possibly more difficult to hear. We want them to be (on average) closer to the size of the taller wave forms.
What we definitely wouldn't want to do is touch the volume slider to the left at the beginning of the track, right under the mute and solo buttons. This will increase the volume on everything for that track, not just the section we're looking for.
To increase the volume of just a portion of your audio, you would select the area you need to level, then choose the Effect drop down, and select the first option called Amplify.
Noise removal is an extremely handy tool to have if you're an indie voice actor trying to record in your room, or maybe a closet if you're lucky. No matter how good of a mic you have, you'll still be picking up some tones from your room and recording space because your mic is an unbiased listener that can't tune out additional sounds the way our ears can. Noise usually comes in as just a low level rumble in the background, or sounds like a hiss behind your words. Some noise is okay, but normally, clients like to have as little of it as possible so they can have a consistent sound if they're using other voice actors, or so they can edit and manipulate your voice without the room coming along with you.
Audacity does have a noise removal option, but I've never been able to get it to work for me in a way that I'm happy with. There is too much of a sound called aliasing, which is caused by the program trying to approximate silence based on what it hears of the noise in the background. Because it's a simple program, it's not very precise, and so you hear a metalic or "sparkly" type effect in the background that is the computer trying to mask the noise and create it's own pretend silence to varying degrees of success.
When I've finished recording and editing in Audacity, I always export my files out (which I'll cover more in the next article) and bring them over to a second program called Wavepad to do noise removal. Wavepad has a free version of their software for non professionals and while I've found it clunky for recording and editing, they do have a superb noise removal tool that is so good for beginners and amateurs that it's worth a few extra steps to use.
After dragging and dropping my exported audio from Audacity into Wavepad, you simply select the Effects tab, then choose the option for Cleanup. Under the Cleanup dropdown, select Noise Removal, then Noise Gate.