Following the first part I present to you part 2 of my series of "Tips for Efficient Roleplay". Please note that these tips are based on my own personal opinions on how you should handle roleplaying in your chosen game.
DO - Roleplay publically even if you're in an instance group. Sometimes other roleplayers will join in if they are present and you will find the experience more enjoyable.
DON'T - Join a random pick-up group and start blathering on in character about being in an instance. It ruins the immersion not only for yourself but also makes you look weird. Either stay in character or stick to a more out of character approach.
DO - Make small-talk about the various things you see in the world. This can sometimes lead to bigger things including large-scale player-driven events specifically for whatever is going on.
DON'T - Insist on commenting on every single thing happening. Most likely your character will be more concerned with a couple things going on and not the entire world. Unless your character is a god you probably won't know every little bit of information out there.
DO - Love your character. Love that you've taken a bunch of pixels and personalized them to be that person you've imagined for your adventures.
DON'T - Be IN LOVE with your character. Last time I checked narcisism was out.
DO - Show off your character's gear in character. Go into great detail about how you slew the beast and skinned it, brought it's hide to the leatherworker and had him make you a beautiful chest piece. Show of that giant fiery sword and be proud, you've earned a bit of glory.
DON'T - Assume anyone will really care. Sometimes people just don't really care about the basic game mechanics even if cleverly written into a story. Getting gear is a very common practice for most people.
DO - Enjoy seclusion. Find the deepest, darkest cave and spend days there. If your character prefers to stay in one place, stay there!
DON'T - Claim you own the cave you're currently "living" in. Most likely there's something bigger than you still inside.
DO - Eat the purple mushrooms.
DON'T - Get angry if you die from them.
Try not to play the commonly known role of a "god-moder". Your character isn't invincible and still must play by the rules of fate. Know that some guilds or groups expect a character to stay lost, kidnapped or dead. Final death is inevitable, so try to stay alive!