When you first start watching the acclaimed "Mad Men" television series, you notice (aside from the fantastic suits and dresses) how different advertising and marketing in the 1960s is from today. Today, such crazy office relationships, three-martini lunches, and raging sexism would result in immediate trips to Human Resources.

But stick with the show long enough, and you'll see that some old-school marketing and advertising ideas are still used today. (No marketing or advertising person's education would be complete without knowing about David Ogilvy or Leo Burnett.)

"Over the last 50 years, many of these fundamental sales strategies have remained incredibly valuable," according to the Leads360 infographic, below, highlighting the evolution of sales since the Mad Men era.

In the 1960s, the sales profession focused on in-person pitching. Nowadays, thanks to technology, people can pitch from a distance via email, Skype, Google Hangout, and so on. What hasn't changed is the focus on the customers' needs.

Sales in the 1970s are best remembered as the age of the door-to-door vacuum cleaner pitch. A sales professional came to a person's house, touted the vacuum's amazing cleaning powers, and demonstrated its capabilities by first tossing dirt on the carpet then vacuuming it all up.

These days, you most likely won't have to knock on someone's door and show them your product in person, but you still should possess the same fervor and belief in your product that the 1970s vacuum salesman did.

With the Internet age dawning in the early 1990s, salespeople focused primarily on email messaging. By the late 1990s, some 85% of companies began using CRM (customer relationship management) tools to keep their prospect info in one place. Today, email remains as popular than ever, though modern marketers are savvier about email and user profiles and click-through rates.

So, how is the sales profession in the 2000s? Check out the following infographic to find out.