Baldur's Gate 3 is three acts, and the most common way to have a worse time is to rush through Act 1 before it is finished. The game front-loads a great deal of content and most of it never becomes available again.
Spoiler-light below: locations and sequencing only.
Act 1: the Wilderness
You wake on a beach. Recruit everyone you meet, because companions are gated by proximity and missing one costs their entire questline.
Clear the Emerald Grove area thoroughly before advancing anything that looks like a climax. The Grove, the Blighted Village, the Goblin Camp and the surrounding map hold more content than the critical path suggests.
The Underdark and the Mountain Pass are both routes onward. You can do both, and you should, but the game does not tell you that clearly. Do the Underdark first.
Level 5 is the biggest power jump in the game. Reach it before leaving Act 1.
Act 1 side content worth not missing
The Zhentarim hideout, the Arcane Tower in the Underdark, and the Grymforge sequence.
Anything requiring you to make a decision about the Grove is a fork with consequences that follow you to Act 3. Take your time on it.
Act 2: the Shadow-Cursed Lands
Darkness is a mechanic here rather than a mood. You need light sources or the appropriate protection to move safely, and getting it is the first objective.
Last Light Inn is the hub. Everything radiates from there.
This act is the shortest and the most linear. It is also the one where companion approval decisions land hardest, so talk to everyone at camp after each major beat.
Act 3: Baldur's Gate
The city is enormous and the quest log becomes overwhelming. Some quests soft-lock if you advance the main story too far, which is the most common complaint about the act.
Clear the Lower City side content before pushing the main quest past the halfway mark. If you are unsure whether something is a point of no return, the game usually warns you, and the warnings are worth believing here.
The Wyrmway, the Iron Throne, and the House of Hope are all optional and all substantial.
General advice that saves runs
Long rest often. Camp scenes are content, and rationing supplies means missing them.
Save before every conversation that looks important, because dialogue outcomes are not always recoverable.
Read item descriptions. Act 3 in particular hides equipment that changes builds entirely.
Points of no return, roughly
Each act ends with a transition you cannot reverse, and each one strands unfinished content behind it.
Leaving Act 1 closes the Grove, the Goblin Camp and the Underdark. Leaving Act 2 closes Last Light and everything in the Shadow-Cursed Lands. In Act 3 the lock-outs are internal to the act and tied to how far the main quest has progressed rather than to leaving.
The game warns you before each one. Take the warning as a genuine instruction to go and finish what is open.
Difficulty, honestly
Balanced is tuned for players comfortable with 5th edition rules. Explorer removes most of the challenge and is a fine way to play for the story.
Tactician is where the build advice starts mattering, and Honour Mode adds a single save file plus boss abilities that do not exist elsewhere. Do not attempt Honour Mode on a first playthrough. The legendary actions genuinely change the fights and there is no learning by dying.
The Baldur's Gate 3 builds guide covers multiclassing and the action economy.
