There are days when I want to rip my mouth off and flush it down the toilet. Mouth noise is the bane of my existence (one of them, anyway). Over the long, winding course of my now-several-months-long career, I've found a few practices and tricks to reduce or eliminate those annoying pops, clicks, whirrs, and ca-chunk-a-chunks your mouth makes. NOTE: If your mouth is ca-chunk-a-chunking involuntarily, please consult a doctor that specializes in face carburetors.
For the clicks created by spittle on your gums, eat an apple. No, a green one. I know you like honeycrisps better, but trust me. The juice from sour apples will burn off the spittle and reduce your saliva production, allowing you to speak high consonants without any troublesome noise. This trick has saved me from a meltdown in-studio once or twice. Ah, breathing. You necessary, no-you-no-life little punk. I've been playing around with my breathing since I first started voice acting all those days ago. First lesson was to stop breathing through my nose. It's way sharper, not that much faster, and sounds really obvious and terrible when picked up. Next is to breathe with your diaphragm. Pulling air into your belly will make you avoid sucking in air, which in turn makes you avoid the sound of sucking in air.To reduce the impact of plosives (p- sounds, hard f's, any other morpheme, phoneme, or diphthong that sounds like you just blew hot air straight into the mic), experiment with setting your mic off-axis. Most decent wide condenser mics will have a wide cardioid pattern, meaning you can move around a bit and still capture clear sound. Put your mic a little to the side to avoid blowing directly into it. This should also help a bit with breathing. Check out this video for a longer explanation of this.
This next sound's a little difficult to explain. It sounds like you're kind of clearing your nose, like a short snore or like you're getting ready to spit. I notice this happens when I accidentally push a little air into my nose, which causes a sound not unlike blowing my nose in the distance. Just concentrate on where your air is supposed to go and keep it even and well-supplied. Don't swallow your breath, if that makes any sense. Here are a few breathing lessons to practice.
Those are the biggest problematic sounds coming out of my face so far. You know, other than all those words and sentences I keep spouting. More on those later!