I semi-regularly read Boldmethod articles, which is an aviation site geared towards real world flying. Although it is geared towards flying in the real world, it can be extremely educational to those trying to figure things out on Vatsim. There is a lot of really good information here and I highly suggest checking it out.
I came across this article today called "6 Ways To Improve Your Radio Calls" and I thought this would be very helpful to the Vatsim pilot. I'd only say, for number 5, find a spot that your not eating your mic, and it is also not too far away. The mics on a real headset are different than what we have on our computers.
Happy reading!
http://www.boldmethod.com/blog/lists/2017/05/6-ways-to-improve-your-radio-calls/