The Don't's
Swearing - You’ll probably swear a lot to start with, but try to keep it under control. You’ll just impress the 12 year olds with huge swearing rants but it becomes grating if it's the only string to your bow.

Calling the wrong play - You aren’t going to see every single play ever, tf2 is like a football match with 12 balls on the pitch so you’re bound to make a few mistakes. It’s fine, you’re new, but learn fast!

Over projecting - A common issue for new commentators as they often try to inject an almost false level of excitement by being loud at the wrong moments. Focus on bringing as honest coverage as you can provide and over time you’ll understand when to project and at what points they are valuable

Repeating - Using the same words over and over - Another problem that comes up a lot, especially for non-native speakers, and not only for new
commentators.

Remaining Neutral - Got an opinion on something? Share it with your audience and encourage them to debate it in between the games - it really does help the quality of the cast for everyone, including yourself. Don’t
be afraid of being controversial, but avoid being controversial for
the sake of it - you will soon get found out as a fraud.

The Do's
Practice - Some people will start off better than others, some will progress quicker than others, but everyone gets better the more you do it. "Practice, Practice, Practise" - Fatal1ty

Prepare - Most of this gets shrugged off nowadays for the wing-it attitude of tf2 casting and there will be plenty of times where you'll think wasted so much effort on something that you didn't end up needing but I swear there will be times you wished you prepared and had all the information with you. Remember the viewer or listener is relying on you, and will often put a lot of faith in you for information on the players, the teams, their backgrounds and the stories around them. They’re relying on you to make these virtual characters come to life, and for you to humanise what, to the outsider, looks like a very non-human sport.

Play / Learn the Game - Soak yourself in the meta, the strategy, the woes, the highs, of being one of those players playing, not only will this make you better at analysis but allows you be that guide to fans outside of the comp tf2 about what these players are feeling or been through. and allows current comp players to relate to things you inject into your cast