Collect all Audio Diaries in Burial at Sea - Episode 1.
There are 17 audio dairies to collect in this DLC. They're not terribly hard to find. Where you might have trouble are the diaries behind doors that require lock picks to open. If you don't find enough lockpicks, you'll have to backtrack later.
If you're the type to explore every nook and cranny, this shouldn't be too hard for you. Below is a complete video of audio log locations, along with locations of lock picks that you'll need for a handful of diaries.
Don't worry too much about missing a couple. The DLC is fairly short, and you can reload previous chapters to claim any you've missed. You can check which ones you've already collected by hitting and cycling to audio logs.
Be sure to take note of which ones you already have before reloading! When reloading chapters, any audio logs collected after that chapter reappear in the game and don't appear in your audio log history. You are still able to unlock the achievement by collecting only the ones you've missed.
#8 if you only found 3 there is absolutely no chance you even attempted finding them. You would literally have to go out of your way to not find more than 3. Some gamers have different preferences....rushing games on purpose....I shall never understand...
For the record Bioshock wouldnt be Bioshock without the audio diaries. The ones in Infinite were not as good as the first two that is true but...I loved listening to them and being able to visualize the people recording them living in the area I am exploring being able to visualize what they are talking about on the tape perfectly. It gives the game that awesome atmospheric feel to it.
FYI, you do not need to collect them all in one run-through. My first pass I missed 5. After collecting 12 total on my second run-through, which included those 5 I missed previously, I got the achievement.
If you take your time on episode one and enjoy it, you can easily find all the diaries in one go. The only one I missed was in the safe (3 picks) outside of the store that you get shock jockey in. Make sure you get this one the first time, or use shock jockey on the elevator so you're able to get back there if you don't have enough picks. The original way up is only accessible the first time due to an air lock bug, and the only way around it is if you used the elevator. I would have got them all in one go if it let me back up, but sadly I ran into the bug before I knew about it :/