The Guide is the first NPC that the player will encounter in any given world. Unlike other NPCs, he does not need a house, but will move into the first one built, which will often be yours, or the first house you have explored; floating islands or the underground houses in giant trees. If the Guide dies before a house is built, he will not respawn until there is a suitable house in the world. Occasionally, the Guide will walk off cliffs or directly into caves without looking.
The Guide provides tips to new players in order to help them learn the basics of the game. After every available tip has been said, he will cycle through them again.
The Guide will also gives all crafting recipes for any item that the player shows him via the "Crafting" option.
"Greetings, <player name>. Is there something I can help you with?"
"I am here to give you advice on what to do next. It is recommended that you talk with me anytime you get stuck."
"They say there is a person who will tell you how to survive in this land... oh wait. That's me."
The Guide has a tendency to get stuck in caves, holes, etc. To avoid this, cover up any holes or caves within the Guide's area or just cover him up until you build a house for him.
In previous versions of the game, the Guide would wander around even at night, opening doors and letting hostile mobs in.
The Guide's hair seems to be a deformed version of Hair 2.
In the iOS version of Terraria, the Guide can no longer tell you crafting recipes. The recipes that include any or all of your items you have are displayed when you are crafting.
There is a painting in the game that appears to be the Guide called Guide Picasso.
The Guide will take damage from things like the Rainbow Gun if you equip the Guide Voodoo Doll after you cast the spell. If you remove the Doll, it will immediatly stop the damage.
The only time the Guide asks a question is on Blood Moons when he asks if the player has seen any Deathweed.
If the Guide's name is Andrew he will drop a Green Cap when killed, most likely a reference to Andrew being Redigit's real name.
Like any other NPC, the Guide won't respawn if there are any world events (like Goblin Attack) ongoing.
It's possible he will be named Guide the Guide instead of the names above.
Sometimes the Guide will say "Hang on to any bombs you might find. A Demolitionist may want to to take a look at them" when the Demolitionist is already present.
Sometimes the Guide will automatically craft an item using your items when asking for a recipe. (Console only)
Sometimes the Guide might not spawn back too fast or never.
On the mobile versions, the Guide can say "You should make an attempt to max out your available life. Try to gather 20 hearts.", while you can only have a maximum of 10 hearts (200 health) yet he still says it.
On the Mobile Versions, when the Guide respawns after being killed in the summoning of the Wall of Flesh, the player will be able to kill him normally without having a special weapon equipped or having a Guide Voodoo Doll equiped. This can usually be fixed by exiting and re-entering the world or by waiting it out.
When the hunter potion is used the Guide will light up, It appears that the Merchant is the only pre-hard mode NPC that won't light up.
Even thought your world has been summoned with The Crimson instead of The Corruption, the Guide will keep telling you to destroy "Shadow Orbs" on the Corruption, despite having destroyed many Pulsating Hearts.