nervous incoming SA

For once the Monkey Bot gave a pretty decent answer.

I'll only add my personal take on your questions below, but genuinely the MB version above is not a bad high-level view:

1. Independent working - Frankly, for an SA it's a non-issue really, since you'll have to be told what to do, so not exactly a deal breaker. However, to showcase that you can do more than what you're told, you can:
   • Engage your supervisor early & often: align with them on process + output and if you hit a roadblock of some sort, try to invest some time trying to solve it, and if you cannot, seek their advice, prefacing that you have tried XYZ and think maybe ABC could also work, but you'd like their input
   • Workplan a little bit: every day you'll have a series of tasks / to-do's to perform, of course you'll be told what to do, but if you can invest ~15-20mins every morning to think about your day and where you think you should invest your time and efforts, that'd be great. It does not matter at all how right/wrong you are, only matters that you do it (getting better comes later with experience + feedback)
   • Update your supervisor with EOD notes: at the end of each day, prepare 3-5 bullet points on what you completed on the day + any new insights gathered that are relevant and share some potential next steps for the following day (usually follows logically from whatever you were doing before + wherever the team happens to be at). That will be a great recap for you & your supervisor. A simple ping on Teams or via email is best
2. Speaking skillls - This will come with practice, simple as. And yes, consultants do end up doing Top-Down communication all the time and signposting everything they say (force of habit). The Pyramid principle is your friend: Main Message first, then main supporting arguments (signposted: "Three things Id like to talk about", "First", "Second", Finally"), and then circling back and deep-diving where most relevant. Practice, practice, practice. Your writing here is structured well enough, so you clearly get it. Just need to do it all the time now :D
3. Zero Defect - We call it zero defect (ZD) at Bain, but that's the same thing: minimise errors (to 0 if possible). The simplest way to do it is to build a process for yourself:
   • In an Excel model, have clean tables with clear labels, that all match each other across sheets, and build checks (e.g. percent totals = 100%, or Revenue across Geos = Revenue across Product Lines, etc.), making sure that two things that should be equal to each other, are indeed equal. Very important, and builds trust
   • In PowerPoint, have a set checking process as you build / update a slide: do all the numbers tie up? Did anything change here that impacts something elsewhere? Did anything change elsewhere that impacts this slide? Does the tag still make sense with the content of the slide after updating it? Are the sources correct?
   • Truth is, the easiest way to simplify checks later on is to reduce the need for them.... so basically, as soon as you write something CHECK it. You re-wrote a paragraph? Re-read it NOW. You changed a figure in the data row of your graph? CHECK if it impacts ANYTHING on the slide or elsewhere. You added a new insight or piece of data on the slide? ADD the source NOW
     • I suck at ZD personally, so I try to minimise the need for it down the line (nothing worse than re-reading the same 15 slides at midnight trying to catch typos) 
4. Expectations - Honestly, expectations are pretty low of SAs, as long as you don't ruin anything. Perfect analysis? No one expects that from you, but if you can do it, it's a big plus for everyone. Perfect slides? Definitely not expected, as even first-year FT employees aren't there, often. But do try to minimise errors. The best way to produce high quality output is to be diligent, have a repeatable process (eg for building an Excel model, for checking a slide, etc.), and to document everything you find (if you see a good data point online, screenshot it, put it in a OneNote and copy the URL, as someone might ask you for it 2-3 days later)
5. Above & Beyond - To me it's about doing more than what you were asked. Everyone can do what they're told, but not everyone does that one bit extra. It can take many forms:
   • Offering to help out the team when you're done with your tasks. I do that often, especially when I happen to finish early. My philosophy is that if I can invest 30mins of my time and help you get out 30-45mins earlier, I should at least offer. They may very well say no (for various reasons), but they'll always appreciate the offer. And sometimes you can be helpful and help out a bit
   • Volunteering to (1) take notes during meetings you're attending but aren't sure what you're doing there or to (2) organise social events for the team if there are any, such as team events or lunches
   • (rarely, because more difficult without much experience) Suggesting a different idea / approach for a given task if you think there's a possibly better / faster way to do it, or some extra piece of work that could be done to strengthen an argument

Now, regarding your reasons to be nervous, it's luckily very simple. You cannot control the economy, but if you work well with your colleagues and do a good job, your odds of getting a return offer increase dramatically. So, work well this summer, be diligent, focused, and also be yourself (no one likes to work with a robot).

As for your other 2 comments, I can understand why you'd feel that way, and I commend you for not being cocky or arrogant. Humility is a quality I certainly value a lot, but do not let it drag you down and not feel confident about your abilities. It's very hard to "con" major consulting firms, even at the recruiting stage. By and large, everyone hired has the skillset to succeed, what happens afterward is dependent on too many factors to count.

If you made it, you made it. Leave it at that. Not sure if it'll mean anything to you, but I have met people with imposter syndrome at Bain all the way up to Associate Partner. It's natural, You're surrounded by very capable people, and hardly anyone of them publicly voices how unconfident they feel. However, rest assured that many also feel that way (including experienced consultants, managers, and principals).

I feel it too sometimes, but I don't let it bother me because I just focus on what I'm doing. I do the best I can with what I have in front of me, I take feedback seriously, and I move on. If you did your best, you have nothing to be ashamed of nor regret.

Best of luck to you!

PS: here are some additional work-related advice I gave a while back - LINK (others also added some good advice on there too, so read on)