Most achievements you will get automatically by simply playing the game, because they are story oriented or you obtain them for defeating enemies (First Kills Are Special, Who's the Hunter Now?, Seeing Red) or bosses (Not Waiting to Exhale, Giant Snake Got Nothin', Deep Sixed, Spider Sense, Grave Digger). Keep in mind that you might skip both Black Tiger and first Yawn boss fight but then you won't get achievements for them (Not Waiting to Exhale and Spider Sense).
There are few achievements that require rescuing Barry, Chris and/or Richard. You may also hunt for achievement for finishing the game without rescuing Chris and Barry, but it's not worth it right now (3 achievements vs 1).
You also get one achievement for dying - but you will surely do this at least once anyway
If you finish the game as Jill on Normal, at the end of the game you will get 4 achievements: for finishing the game as Jill and for finishing the game on very easy, easy and normal difficulty.
Achievements that you can also get on your first playthrough but that require some more work are:
- Every Nook and Cranny - visit all places on all maps and pick up every single item; basically, before leaving an area check on map if all rooms on the map are marked as green. If they are red - that means there's something to pick up there.
- Racing and Pacing - finish the game in five hours (I doubt you will get it on your first try, especially if this is your first time with the game and you also want to get Every Nook and Cranny, but good luck
)
- Break Out the Marshmallows! - burn up two zombies at the smae time with the lighter
Other achievements require you to either play the game as Chris, play without rescuing anyone (for both Chris and Jill), play using special modes or doing speedrun (under 3h), knife only runs or no save runs.