DOs and DON'Ts of a programming class?

I hope this will be of some help to you - I used to head TA a CS course at an Ivy League college, which mean I wrote the mark schemes and grading guidelines.

Firstly, everyone does things differently, and in all honesty grading code is as subjective as grading an essay (this always surprises students starting out, because many think writing code is more akin to solving a maths problem). I fully expect people here to disagree with some of my thoughts, mainly because it is just so subjective.

Commenting: my personal opinion was always that code should be self documenting. For example, bad commenting would be as follows:

// For loop to iterate through numbers    
for (int i = 0; i < 5; i++) {
         NSLog(@"%d", i*i); // Prints the result
    }

Hopefully I don't need to explain why that's bad, but just in case - it's pretty obvious what it does, and furthermore the comments don't actually add anything useful.

Moving on to code style: check with your course. If your course has a particular style that's preferred, you should obviously use it. If not, my own attitude was to generally be fairly flexible - as long as you, the student, were consistent from assignment to assignment (enforcing consistency also makes it easier to pick up when someone is cheating).

Finally, as you're probably realising, not every professor does things 'by the book', for better or for worse. They may have their own reasons for doing this, or they may simply be poor. Since your stated goal is to achieve an A (in all honesty, I was always a little disappointed in students who came into courses with a grade in mind, but I understand why GPA can be important to people), you just need to play the system. You could see some truly horrible things being taught, but your goal is to get the highest grade possible. To do that, you'll need to play things by the book, regardless of 'right' or 'wrong' (horribly cynical point: it always helps to make yourself known to course staff, through office hours or similar, because whoever grades you will perhaps be a little more sympathetic. Unless of course you're a total sociopath, but I'm going to assume not! :))