Being a good Commander in WvW requires you to be good at many different skill sets. Not only will you need to be familiar with the maps, tactics and the art of war, you will also need to be familiar with how to get people to follow you and listen to you. Being bad at one of these things will make you a bad Commander. I don't say that to be rude or discourage you, I say it as a warning before you go and drop 100g on something you may never use or even get screamed at for turning on.
Now before you even think about commanding you will need to learn all of the basics and intermediary parts of WvW. You're obviously not going to be able to be a complete noob and expect to lead people to success. Of course as a Commander there will be things you don't know, don't worry about them and be upfront and honest with those you are leading if you're unfamiliar with something. For example, I am ignorant when it comes to Trebs and when it comes to needing to use one or place one to hit a certain target I ask for advice.
This guide is split into two key parts. One is going to be a text based guide. All of the information you need can be found via the text on this page or, if you would prefer watching a video below I have a video on How to be a good Commander which is 12 minutes long going over everything I go over on this page. To view the video click on the link in this paragraph or on the embedded video below. To continue down to the text version of this guide scroll past the video and let's get started!
1. Bring your own siege. - This is an important one since a lot of the time no one will reliably drop siege for you and/or they just wont have siege to drop. As a Commander you will need to make sure you always have what it takes to successfully take the target you're after.
2. Always tell the raid force you're leading what to do one move ahead. - This will help keep the raid focused on the task at hand. If you are always giving them something to do then there will be no time for them to go do something stupid that they shouldn't be doing.
3. Keep people highly informed (Always keep them looking at chat). - Keeping people informed and watching chat will make sure they continue to obey your orders.
4. Give your orders in /say when you're around your raid group - people have Tunnel Vision! - If you need a group of people around you to grab supply, build some siege or stop chasing some enemy into their territory make sure you give the order in /say that way they see it in the middle of their screen.
5. Be a good leader - You'll need leadership qualities to successfully lead WvW. Knowing how to get people to listen and pay attention amongst other things is very important. - Not only do you need to be familiar with tactics in WvW you will also need to know how to get people to listen to the orders you are giving. If people don't listen to you it doesn't matter how good you are.
6. Make sure you sound confident. Don't let the trolls make you second guess yourself. If you show weakness or lack confidence it will show in your leadership. - If you let the trolls get to you and start second guessing or questioning your own orders you will lose the faith and trust of your zerglings.
7. Being a Commander is expensive! - Make sure you have a lot of gold not only to buy the Commander tag but to keep buying siege every time you need it.
8. If you are not a Commander and reading this, help them out by saying orders in /say (tell people when to supply, tell them not to chase enemies, tell them to follow the commander when he leaves an area etc) ONLY REINFORCE HIS COMMANDS - DON'T GIVE YOUR OWN ORDERS