As a busy hiring manager in startups, I've often felt impatient with or lost interest in candidates who ramble in their answers or overstate their knowledge, so my best advice would be to strive to be concise and humble.
This might sound counter-intuitive as you might want to list all the ways in which you are a great candidate for a position, but in reality, most good hiring managers are very busy and can smell baloney.
Interviewers have a lot of things on their mind and if you can't answer their questions clearly and concisely, they can get frustrated and loose interest. Resist the temptation to provide a lot of context or go into great details (unless asked). Some candidates might be long-winded unconsciously because they’re anxious, intimidated and/or afraid of messing up in front of those they’re trying to impress, so you need to watch for signs when it's happening. Try to provide a clear and succinct answer to the point and then pause. Breathe, and look for a feedback cue. If the Interviewers want to hear more, they'll ask a question or appear attentive. If they move on, they are satisfied and you should let it be.
Experienced hiring managers will also be able to tell if you are exaggerating your knowledge or experience. They might get clues from the lack of specifics or ask follow up questions you can't answer well. If that happens, you've lost their trust and that is a red flag. If you’re struggling to come up with a suitable response to an interview question, it can be tempting to resort to inventing an anecdote out of thin air. In the moment, it might feel preferable to come up empty, but it is wiser to maintain a balance between confidence in your own abilities and humility, which means knowing when to say I don't know. It doesn't have to be a defeatist answer. You might say you didn't have the opportunity to work on this or share challenges you faced in this area, but it's something you're really interested in learning or building experience in.
Have you caught yourself rambling during interviews?