Summarize:

The established rules on etiquette, or expected politeness, will vary based on whichever people you are spending time with. When all else fails, reading up on proper etiquette is a good idea. Although the idea of "proper etiquette" is associated with the outdated Victorian period, a lot of the customs still hold up in the current period. If you're any bit unsure, its better to adhere to a custom than to ignore it. Politeness is no less important today than it was back then, and there are new rules that should be observed in modern times. Generally speaking, keep your phone out of sight when you're talking to someone. Give the other person ample time to finish what they have to say. Invest yourself in whatever the other person is saying. Even if you're not so interested in what they're saying, you won't do yourself any favours by acting unimpressed. Always remember to say please and thank you. These tricks have never lost any favour over the years. Not coming across as being rude is made all the more challenging if you're talking to someone who is naturally sensitive. Emotional sensitivity should be seen as a good thing in most instances, but it can be tricky if you're talking to someone who might get hurt by the slightest grievance. If you think this is the case with someone, it's a good thing to know what their personal preferences are before going into an extended conversation with them. For instance, if you think someone isn't likely to enjoy crude humour, it's best to hold off on it until they're out of your company. Asking about someone beforehand can give you the edge you need in a conversation if politeness is an issue. Ask about their preferences or emotional triggers. Failing that it's always helpful to see the way someone interacts in a social situation before you interact with the person yourself. Even if it doesn't involve a direct action on your part, a lot of rudeness can be evaded completely through empathy and knowing how the other person is feeling while you're talking. Because people can be tricky on this front, your best option is to try and gauge how they're feeling through non-verbal communication. Make a habit of paying attention to someone's facial expression while they talk. Sometimes, what they're saying won't match up to the mood their expression is hinting at. Unfortunately, asking "How are you feeling" won't result in a sincere report from most people. People aren't trained to report their feelings accurately. Others may feel embarrassed or unwilling to show their true feelings. A lot of what someone considers to be rude has to do with the culture they were raised in. If you're going to be travelling or regularly deal with people who were raised in other cultures, it's a good idea to verse yourself on what is and isn't appropriate in their eyes. Although people are usually accustomed to getting past these cultural differences, the simple act of looking into these customs beforehand will be seen as very gracious on your part. As with most social interactions, the way you act needs to be informed by the circumstances of your situation. In other words, the way you demonstrate respect and politeness will differ depending on whether you're at a wedding, funeral, or a casual night out. Politeness means being self-aware and tactful. If you're acting cheery at a funeral wake, it will evoke the same negative reactions as if you were being glum at a birthday party. This should also include your dress and appearance. People will judge you a lot based on the way you make yourself appear. If you're ever unsure about which particular way you should be acting in a social setting, it's a good idea to try copying what other people are generally doing. If you really want to leave an impression as a polite and tactful individual, you can't rely on politeness for the short-term. Politeness can't be an act. Rather, it needs to be a constant state of mind. Keep your behaviour consistent. If someone sees two different sides of you, you'll appear all the more phoney to them.
Learn up on etiquette. Consider the other person's sensitivities. Gauge how the other person is feeling. Take culture into account. Act to fit your surroundings. Keep your politeness consistent.