I completed the game, going clean through the audit and retaining my work, while having 400 credits on the last day.
Here are my thoughts and advice for anyone attempting their first run.

1) Take your time to make a convenient list of the main information otherwise hidden in the rulebook. You want at least the issuing cities and the districts of Arstotzka, since that information is relevant most often and is hidden very deep. Make sure your eyes will have to travel a minimum distance from the game area to the list. My solution was to run the game in a window and have a word file open next to it.
2) Prepare your workplace for work every day before you open the gates - have the rulebook open on the basic rules page and the criminals bulletin next to it, once it is available.
3) Every day when you have to work with a new document, take your time to construct a new "eye route". That is, experiment with the layout of documents on your desk and the way to check information in them, which demands the least eye movement. Then restart the day and blaze through.
4) Use the logic of the game to your advantage. In non-scripted encounters there is a maximum of one of each - lacking document, discrepancy in the documents and discrepancy in the interrogation. So if you have already found and resolved one discrepancy in the documents, you can stop looking for others. This saves a lot of time.
5) Don't waste time explaining the discrepancy until you are actually required to do so. Just stamp away.
6) Buy the first three booth upgrades as soon as prompted. They contribute significantly to your speed.
7) Once you get a gun, make your shots quick and make them count.
8) Detain people when prompted. At least after the guard moves to the prison.
9) There are exactly two times in the game when you HAVE to break the rules. If you aim for the 20th ending don't break them elsewhere.
10) I was going through my game alternating food and heat consumption to save money and ended with a 400 credits proficit, while buying everything when prompted. It should be possible to complete the game without limiting yourself at all, but you'd have to exceed my average of 16 applicants per quiet day or abstain from moving to level 5 apartments.

Exactly.

For my run, for the 20th ending, act as truthful and loyal to Arstotzka as you can, like a good little soldier(or suck up for that matter).

Saving money, I would alternate the food consumption for the family. Thats a saving of 15 bucks (your kid is going to get sick the other day so -5 bucks) every 2 days.

Here's a link to a great reference for this sort of information. I didn't make it, but he's credited on the image.

Helpful guide.

As far as I can tell, moving up to new apartments has no impact on the ending, and you can keep your family in good health in a class 8 or 7, so long as you average 10-12 people a day and detain people most times you're given a chance.

Breaking the rules here and there is okay, (I let the occasional sob story get to me) but do NOT assist Ezic.

what counts as assisting the ezic? for example, if you give the "drex corman" note and get the coded message, does that count?

No. In fact, giving the note back is required to progress. Basically, whenever you receive an order from EZIC, do the opposite.

I have extra tips for 20th ending (I finished with 1060 credits):
- Day 1 is a great opportunity for lots of money, since you only have to check the country.
- In general, don't detain until you get the REASON stamp. If you're efficient enough (aka stamping without using the inconsistencies tool), it turns out that the time it takes for the guards to intervene twice is slower than the average time it takes to process one person.
- Remember the seals, the list of Arstotzka districts and the lists of issuing cities with their associated countries by heart. Practice using the poster in GOG's bonus content. There are a few tricks that can help. For example, Impor has Japanese-sounding names, and the same 2 seals are shared for all documents except for work passes.
- Whenever you hear a bike, stop what you're doing and get the key to your gun ready.
- If you click on an empty spot when you start saying "Papers, please.", the current immigrant will drop his papers quicker in your booth.
- Whenever an EZIC agent drops a "read quickly" letter, just open it and immediately give it back. You don't even need to know the letter contents if you're not helping them.

I concur. Although I could not be bothered to actually learn anything by heart.
How many applicants did you review per day on average to finish with a 1000+ proficit?
Or did you simply limit your shopping?

I did a perfect 2-citations run while alternating between no food and no heat and without moving apartments. As far as I know, acquiring tokens or moving apartment classes is completely useless so I didn't bother. I probably will for my next playthrough though.

As for my efficiency, excluding scripted events, I can process in average 13 immigrants without mistakes in 10 minutes with the final ruleset.

Good tips. Few thing come to mind.

-I find it convenient to place the passport directly under the 'approved' or 'denied' stamp. I placed the passport under 'approved' since you can often just detain people with discrepancies and don't need to stamp 'denied'.

-I usually keep the rulebook open on the work area and return to basic rules page when the next entrant is walking in - those are the ones you'll be referring to constantly. The problem is that small items like the native ID card can get lost behind the rulebook, so I place the rulebook low and ID card over it.

I recently finished my first playthrough and received ending 19/20, much to my satisfaction. It sounds more desireable than the 20/20 ending being talked about.
I helped EZIC every step of the way and they eventually overthrew the oppressive Arstotzkan government, opened the boarder to more people (I let SO MANY people through who would have been denied if I followed the rules, most were good people with slight document problems from shitty governments and they "caused no trouble'), my family was all safe and taken to better living quarters, I got promoted to intelligence work for the new Arstotzkan goverment, and seemingly won the day!

For some reason I got this on my first-ish playthrough.

I say "ish" because I originally expected to be arrested, so I got lots of Obristan passports and escaped. Then when I went back to an earlier save - just to see what would happen if I had stayed - I got the "overthrow" ending.

Although apart from helping Ezic the only people I helped were those that bribed me. If I was going to get reprimanded for letting someone get through who was too lazy to sort out their papers, then the least they could do was 1) admit their mistake (instead of pretending to not notice!) and 2) offer a bribe!

Don't they know I can only afford heat on even numbered days?

Haha! I let everyone through who had a legit-sounding excuse like "but I just got it renewed" and "it must be a mistake" and "my government wouldn't give me the papers," whenever it didn't seem like they were blatantly trying to get away with something (often saying you're passing through when you're actually visiting, depending on the response when I call them on it, is a bit shady), I figured they were just trying to get away from their horrible gov't to somewhere that might be better. I let everyone through whose names had 1 single letter difference. I figure with it being different countries, I should allow for some discrepancy with names (Josef and Josaf or whatever, c'mon, obviously it's the same dude, I fingerprinted him, even if it doesn't say he has another name, it's the same name!) The scripted decisions like bribes and sob-stories I behaved morally (let the woman in with her husband, let the woman in to see her son, let the guy in whose district card was stolen, allowed the dude to kill the child-killer.) I allowed almost every single person from Antegria in unless their story was unbelievable or they had dire discrepancies (different fingerprints, different photo, etc.)

I also didn't confiscate a single Arstotzkan passport.

Wow - that must have surely hurt your paycheck? Especially considering most people don't pay bribes?

Hopefully you never get a job in border security in any country... ;)

I was actually kind of the opposite - more of a total prick in fact - generally if the name's didn't match and the prints didn't confirm the new name, I'd get the dude arrested! First game through, I'd push that arrest button as soon as it popped up.

I think one of the first times I pushed it so fast, there was a guy was offering me a bribe, but I'd already pushed it by the time he said anything... I was mainly bummed about missing out on the bribe, since my family was cold/hungry.

Also I took the bribe from the guy from the sports team, kept the "arsekickers" banner, and when he wanted it back had him arrested too!

Guy who gave me the watch - stole the watch, had him arrested, sold the watch!

I think this game brings out my evil side... ;)

Though I did help out Sergei's girlfriend. Despite the fact the guy can't shoot to save his life (literally).

Unfortunately the guard who gave me the "deal" never quite payed for all those extra incarcerations like he said, otherwise I'd be swimming in it!

Very interesting!

I only had to deny food once (the day before the niece arrives), it made my son sick but the next day with the niece I was able to get him healthy and never had to deny them food. I never denied them heat (omg so cold, you can tell by how ppl were dressed and if you think about it being in the old USSR territories during november/december), despite all the people I let in who were violations. I did try to keep it to 3 acceptable violations per day (so I'd only get fined 5c), but somtimes I let 5 or 6 or 7 through, but I was able to keep the $ up and not have it be too detrimental to me/my family. On non-terrorist attack days I'd usually get 14-16 processed.

Anyone offering a bribe I had detained unless they seemed like a good person that was truly desperate, but most desperate people can't bribe. Gave the guy back his banner, gave the guy his watch, never ever ever let Jorji in (and never detained him.)