Poor microphone technique is signalled by hissing S noises and startling POPs. A low-quality microphone can be blamed for some of that noise, but with a decent mic technique, even a low quality microphone can do the job.
Good technique isn't rocket science. In fact, there are really only a couple of things to know to improve your sound a thousand percent.
Positioning the microphone dead centre in front of your mouth is a big mistake. The idea is to move the mic out of the direct path of air from your mouth as you speak. It doesn't really matter where you move your mic, as long as it's off the beaten path somewhere. I prefer to move my mic an inch or so below my mouth where Kelly prefers to have hers an inch or so above her mouth. If you have a standalone mic rather than a headset/mic then you have even more options.
Pretty much any position out of the path of air will work, but be careful not to jump out of the pot into the kettle. Ensure that your new position doesn't put your mic in the path of air from your nose, or move the mic so far away that you sound like you're in a tin can.
By now I would hope you've listened to at least one of my JaK Attack! podcasts - show #9 is really good :) - and you've likely noticed one thing about me. I speak too fast. Way too fast sometimes. That's poor speaking technique, but I'm working on it. Another thing that I hope you noticed is that there's not a lot of popping and essing going on in the show.
Most of this is due to mic technique, but some of it also comes from an awareness of what I'm saying (even if I am saying it too fast). I'm always aware when I'm saying an 'S' or a word with a lot of popping P's in it. I tone down those words so that the explosion of air is much less.
Experimentation is the key - play around wth different techniques and see what sounds good. Make a note of what works so when you sit down a week later, you'll remember what worked for you.