In my opinion, the best time to get started preparing would be from Summer, if you can manage it with your internship then you can start it then else right after the internships end. Now the steps usually depend on the areas you're targeting. For me that was Consulting and Analytics so I'll talk about that. You can practice guesstimates by yourself but for cases you'll need a case group. You should form a Case Group of about 4 people( including yourself) with whom you can practice the cases. Start with basics like Case Interviews Cracked, Victor Cheng Videos & Day One. Practice profitability cases first and maintain a record of your cases and the feedback you receive. This is pre shortlist practice. After the shortlists are out groups reform and then just try and practice as much with peers and their buddies as well. Analytics is a different ballgame and you need to do well in Aptitude, Quant & Coding to crack the shortlists. For aptitude there are multiple sites which offer practice like pariksha and even OCS had provided some practice. Those who are also doing prep for CAT should do fine as the topics are similar to those asked in the Quant Section of CAT. For the Quant part you need to look at Probability and Statistics, if you've done MTL106, then just briefly revise the concepts. If you've not done it then start with BrainStellar. It has puzzles on different sections, starting with Probability. It has a good set of questions. Apart from that there are certian books which you can do if time permits, 'Heard on the Street', '50 Must Do Probability Qns' and other websites like interviewbit, csblogspot where you can find more material to practice. Now for coding, start practicing with interviewbit where the questions are arranged by their concepts. You can also practice on Leetcode. The level of proficiency you're trying to achieve should be proportional to the companies you're targeting. Generally speaking though it's a good practice to cover all the DSA concepts. If you've done COL106- DSA then it's better. Apart from this just have a look at OOPS, SQL Queries, OS and other such topics which are also asked in tests as MCQs
Q
Comparison between your intern and placement interviews?
The experience was quite different Probably because one of them was in offline mode and the other was in an online mode. In the offline mode it's a lot more chaotic, you've to be present at different locations and also it's a physical interview. Your body language, your dressing sense and all these exterior aspects can also come into play. Also since you're interacting face to face that is better, in online interviews it is tougher to show energy and enthusiasm than in an offline interview. Still I preferred the online interviews because OCS organised it in a really good manner, there wasn't as much chaos as we see in the offline interviews
Q
How did you decide your field of interest? What about backups?
I was primarily interested in Consulting after my third year as it aligned with my interests. Till then I didn't have much coding experience as well and didn't enjoy it because I hadn't tried it before as well. Also I had done an internship at Ernst and Young in a research Consulting role which I liked so that made me further inclined towards Consulting. I was also looking at Finance although very few companies visit IITD who actually offer roles in Finance ( which is understandable). But I had kept Analytics as a safety net because I felt that it was similar to Consulting but it also required a hold on coding and quant. I wasn't too sure about my shortlist chances. I had started preparing for Analytics (Coding, Quant) after my internship, in July and that was a good decision because I didn't get shortlisted in the major consulting firms. Having a backup can be a good decision as it happened for me but it can also distract you from your original targets. So it all depends on you and what you're targeting. Since consulting shortlists can sometimes be random, if you're not too sure about your chances it's better to have a backup.
Q
If someone does not get an intern via OCS in their 3rd year, what should they do?
Try and get at least some experience by applying offline. For Analytics, SDE, Quant you can compensate that with good projects as far as i know. For consulting you should really try and get some experience by applying directly.
Q
Major problems that you faced?
I hadn't done the COL106 course and was not familiar at all with coding so I felt some difficulty in starting again. Initially after you've done basic practice I suggest that you should directly jump to the questions as you solve more you also get a grasp of the different techniques which are used which accelerates your preparation. During tests, I also faced some issues in coding because some companies have a very tight timeline- for instance 2 questions in 30 minutes. These sort of tests were difficult for me in the beginning. You need to be quite fast at coding, these problems aren't too hard generally but it's just about doing them quickly and passing the test cases.
Q
Online vs Offline placements?
From the preparation point of view, offline would probably be better because you're in insti so you get to meet and prep with your group on a daily basis. From consulting pov also the buddy sessions would be better in the offline sem. From the interviews POV, online was better at least for me because as I mentioned before it was much less stressful as they had made slots for R1&R2 which gave you ample time to interview at multiple firms.
Q
Necessities for targeting your field?
For any field that you're targeting you should be proficient in it. For SDE, Data Science you should have the relevant skills or you should start preparing at an appropriate timeline. For Analytics you can prepare even in your job sem. Most of the interview shortlists in these areas are through the tests, so if you're able to crack that then there shouldn't be an issue. Some companies might additionally look at your resume wherein your CG, internship and projects will play a role. But that's hardly the case and even if it is, it's mostly CG based (7,7,5,8,9- these are the thresholds which would depend on the company) For consulting you need to have a good CV as the interview shortlists are done through CV shortlist. To get through this you should ideally have a CV which has three areas where you have a peak. In a typical consulting CV there are 4 sections- Scholastics + CG, Internships, ECA, PORs. You should have 3 sections which are really good, generally speaking.
During the sem, focus more on yourself and your chances than worrying about external factors. This is cliche advice but it can be tough to apply it during the jobsem. Focus on preparing for your target and improving . Also, don't sleep on the HR rounds. Start preparing for those early as well. 5-7 days before the final interviews. Prepare a good introduction as it makes a difference as well as some other basic HR questions. Write them down yourself and read them a few times but don't memorize it.