Hi Riya,
while applying for internships and grad schemes, it’s important to be on your toes all the time with the application deadlines. MNCs like Google, Microsoft, Goldman, JPMC and thousand others keep updating their job portal regularly. The sooner you apply, the better, since they interview candidates on a rolling basis. It’s important to keep an eye on their job openings or being connected to the hiring managers from the firm one way or the other... For start-ups, you could try reaching out to them on LinkedIn and present a case for yourself on why you seem to be a fit for the position. Having worked at a start-up before, I can tell you that there’s always room for talented and intellectual people and the best way to get into the workplace is by directly reaching out to the senior management at the firm. Feel free to drop more questions on this thread. Best of luck!!