In fact, there is only one achievement you can't miss:
End of a Salesman -
You get it when (if) you finish the game.


All other achievements require some optionable actions, so beware - huge SPOILERS ahead!

There is a group of achievements you get by doing what a real-estate salesman does the best: persuading people (that is, mostly talking them out of money).

Salesman
Persuade any one person without using 'Seller Intuition' (i.e. hints that help you in choosing the right approach). There are six persons you are able to persuade (one of them being optionable) - you will get this achievement on any of them, just do not press that big 'Seller Intuition' button. You can either save/load your game before trying different topics, closely watching the person's reaction to your words (mostly eyebrows-raising) - or seek some spoilers below.

Lazy Bum
Your very first (easy and optionable) sales talk.
1) 'Defend', 2) 'Comfortable', 3) 'Ease', 4) any topic

Do You Even Rob, Bro?
Talk the bank robber out of robbing.
1) 'Expose', 2) 'Philosophize', 3) 'Taunt'

Great Commoner
Convince William Jennings Bryan to speak on the event organized by Merrick.
1) 'Placate', 2) 'Awareness', 3) 'Beauty', 4) 'Morals'

You Are Goiing Toupee For That
Talk Freedy out of the money he owed to your new boss.
1) 'Moderate', 2) 'Retribution', 3) 'Violent' or 'Unreasonable', 4) 'Threaten Life'.

Oh My Guard
Persuade the guard to let you board the train.
1) 'Business', 2) 'Conscience', 3) 'Namedrop'

Super Salesman
In addition to the four (or five, if you choose 'Lazy Bum') persons, the last one you are to persuade is George Merrick himself at the very end of the game. You won't get any special achievement for that, as convincing him is the only way to finish the game - but you will get this achievement for persuading everyone in the game without using hints.
1) 'Needed', 2) 'Convince', 3) 'Defend', 4) 'Warn'

Relics of the Present
Stand on West Flagler Street for 2 or 3 minutes, and in addition to three men and three women dressed in different colors, you will eventually see one more man walking by. It is Arthur Jordan, the protagonist of several earlier games made by the author of 'A Golden Wake' - Ben Jordan[www.grundislavgames.com].


Logic King
On the Land Auction, you can choose either persuading one lone man on the right (see Lazy Bum above) or a small crowd of several people on the left. In the latter case, you are given a puzzle - and the achievement if you solve it without using hints.
Just remember to save your game before that choice! Then you can re-load it and try the other way with extra achievement.


Smooth Criminal
After you opened Riley's safe and switched those plans, do not forget to close the safe before leaving!


Filthy Animal
Do not get shot at the Bakery.
That is, when that kind old lady points her gun at Alfie - quickly use that sack nearby, then exit and use the car before she follows you.

History Repeating
On the contrary, this achievement is awarded to those brave (or foolish) souls who waited on the street after running from the bakery long enough to get shot. That's again some reference to a previous game by the author called "Back Door Man".

Professional Poisoner
While in Havana, you have to deal with Umberto on the first try, not wasting more than one pill. That is, after you have discovered that you can't put anything in his drink with him watching you and have talked to Butch, order whiskey (the only dark drink available), make a sign to Butch and place the pill in Umberto's glass.

Darwin Award
And here is another attempt for you to kill Alfie for good - after finding the moonshine shack, covering the chimney and blocking the stills, wait 3-4 minutes inside, and you will be justly awarded.

Brotherly Love
This achievement will pop up after the game ends - but it is triggered much earlier. Just tell Beau all the truth when speaking to him for the last time.


You Might Learn Something
Switch the commentaries 'On' in 'Settings' before starting the game - and you will get this achievement at the very end.


Good Guy
'You remained above negative influence'... This achievement is also awarded at the very end of the game - but I am unsure of what exact choices in the game trigger it.
There are several scenes in the game where you can choose to lie or to tell the truth: 1) Reporting on the last assignment for George, 2) When meeting George at the hotel, 3) Last conversation with Beau (see Brotherly Love), 4) and 5) Confirming facts about your past at the bar in Chapter 4... There is also an option to warn the person who enters the shack not to do that. 'Good Guy' may depend on all (or some) of those cases.