Now not everyone is going to be the same about how they go about this. We are all individuals with our own paths to walk. However I will share my opinions about how it works in my life.
We all filter things we intake.
Sometimes what is said and what we hear can be quite different. It is important when engaged in conversation you listen to what is said. It is also important to take into context who says it. What mental state is that person in is as important as the words they speak. People will often obscure their own truths because they are in an up state or a down state. It is important to ask questions to fill in the background of where someone is coming from. Not with all conversations. Some people are just big on small talk and just want to fill any gaps with words, any words that fill the silence. It is important to understand the difference between a meaningful conversation and gap fillers. Some are more apt to engage in small talk due to their personality type, there's nothing wrong with that, it is just how they are.
Just because someone says something that upsets you or that you disagree with strongly it doesn't have to affect your mood or outlook. That is totally your choice to make, not theirs. You can respond with what you believe to be true without having to belittle/berate them. Perhaps you'll change their mind but likely not if you make them defensive. I can get passionate about my truths at times and recognize this as an area that needs improvement. Not everything I believe is true and everyone else can teach me something I don't know or am misinformed about. Be open minded about concepts or procedures. There are certain universal truths I know and cannot be moved on but in a lot of areas I am open to new ideas. Take all the good you can from others and filter out the bad.
Filter what you meditate on.
Meditating is something everyone does. It's not just some monk on a mountain top that does it. Lets see what the dictionary says about meditation
Meditation: continued or extended thought; reflection; contemplation.
If you continue to think about something bad that happened to you(some argument or miscommunication that happened recently for example) it will just eat away any positive energy you have. It will become bigger than it really is and no matter how many times you replay it, it doesn't become a pleasant thought. If you have an argument with someone perhaps figuring out a way to remedy the situation would be good to think on. Or perhaps you could think of a good memory with that person and meditate on that. Bitterness and frustration do not get better by thinking about them endlessly. They get worse. Often people will replay the negative things that happen to them over and over for years sometimes and it just makes them bitter. I don't want to feel bitter, I'd rather feel better. If your past keeps haunting you in your thought life there is a program called freedom session that can be a big help. Check it out here.
Words that heal vs words that harm.
Measure your words carefully. Depending on the situation your words can make a big difference to diffuse a situation. They can also fan the flames of discontent. Just because you have a thought doesn't mean you have to share it with the world. Some people talk just for the sake of talking, filling the air with noise. If you didn't like a show and the objectionable content you saw then why are you now describing that content to others? Why not talk about something you like if you need to share. If someone is listing complaints about you then probably this isn't the moment to list your complaints about them. Address their concerns as best you can and realize they are only speaking from their own hurt. They may even be right about some of them :)
Spewing bitterness and resentments is like spreading germs. It is contagious. The flip side is to spread love and joy. This is also contagious and infectiously good. Knowing your audience and knowing yourself is a big asset. Reading body language is something everyone can do to a certain point. I'm not saying never ever complain but make sure it is context and to the right person. Also being super cheery with someone who is really hurting can do more harm than good. When someone is venting is not the right time to correct the finer points of what they are saying. Use some discretion.
Don't be a talking head!!
Try to be discerning in your commentary. You don't have to share your opinion on everything. I fall into that category at times and I know that sometimes less is more. The person that says the most often is listened to the least. Words are precious, measure your words carefully. Offering your opinion on everything can lessen your impact when it is something you have meaningful dialogue on to relay.
Let your actions match your words.
Talk is cheap. If you say one thing then in reality do the opposite your words become less and less meaningful. If you talk about having a positive attitude and then complain about everything and everybody your attitude is anything but positive. Actions DO speak louder than words. So don't spend forever talking about change, actually be an active part of that change and you'll gain respect which in turn will gain more than any words could ever do. I love words but words alone don't do anything. They are meaningless without activities that mimic your words.
So meditate on what is good and true, talk less, listen more and walk your talk.