You don't have to take it consecutively, but many people often do take it in chunks. The most common pattern is to take 1 or 2 weeks off at a time. You could also take it one day at a time, say take a few Mondays off. However, taking every Monday off is generally frowned upon.
You can take it whenever you want, so long as you announce it early enough in advance and there is nothing planned at that time that requires you to be there (e.g. "the product is being launched that week").
Normally, the process is that you check your calendar and check with your boss. Once the vacation is approved, you book your flights, etc. Typically, it is extremely unlikely for someone to cancel your vacation after you've booked it. The general consensus is that once the vacation is approved, the manager just has to accept that it will happen.
Basically, it's common sense - don't disrupt the company's work with your vacation, be sensible, announce it early enough in advance.