For experienced TTRPG players do you have any advice for relatively new players on role playing? From the small amount of games I've played I noticed my biggest weakness was thinking of what to say when talking to Npcs. I'm not good at making conversation in game so I end up with generic characters and mostly just responding to questions people ask me.
I’d consider myself an experienced TTRPG gamer, and I do the same thing with a new character. So what I would do is, make up your character at least a few days before. Think about your character as a youth, then at the present time of his or her adventure, and then finally at a much higher level of experience and accomplishments. Once you have a concept of your character, then when you are interacting with others (NPCs or PCs), you’ll think of what kind of behaviors or even responses he or she might make.
I usually pick a trope, an actual person, a character from a movie or book, or a mix of everything and just run with it. See where it leads. Give them goals, fears, preferences, and maybe peeves. Give the character an accent. Just fucking throw shit together and don't be afraid to fuck up a bit.
Try out some different accents and choose one that you think suits your character. Being able to switch from your normal speaking voice to the voice of a character is very, very hand and often makes for even more memorable games. Consider the posture of your character; shoulders back and straight or hunched? Always makes eye contact or seldom makes eye contact? etc.
Also consider the relationship of your character towards all the NPCs in the game and how that affects what you say and HOW you it. Your character might be affectionate to some, neutral towards others, and suspicious of others etc. This can all change depending on how the NPCs react with you, so it's fairly important to take some mental notes or even write stuff down.