The crucial lesson this personal finance guru learned about money from his immigrant parents

As the child of Indian immigrant parents, Ramit Sethi grew up learning that negotiating the price is part of the process of making a purchase.

And sometimes, those negotiations would go on for a while.

"We would spend, I'm not kidding, we spent one week buying a car," Sethi tells CNBC. "We would go to the car dealership, negotiate all day, go home, then come back the next day and do it again."

Negotiating wasn't reserved for the car dealership. Sethi says his mom would negotiate for with Macy's for a discount on the price of a sweater.

Growing up in America, Sethi noticed that his parents were more willing to negotiate than his peers. "Anyone who has an immigrant parent knows exactly what I'm talking about," says Sethi.

Today, 34-year-old Sethi is a personal finance guru and founder of the online personal finance and career resource "I Will Teach You to be Rich" and GrowthLab.com, where entrepreneurs go to launch and grow their online businesses.

Americans are afraid of negotiating because they are worried about being perceived of as cheap. And because they by and large avoid negotiating, they "are horrible at it," says Sethi.

They shouldn't be. By not negotiating, you leave money on the table, says Sethi.

Avoiding negotiating is "going to cost you hundreds of thousands of dollars over your lifetime. I think it's weird not to learn the skill of negotiating," says Sethi.

The best places to negotiate are with cell phone contracts, credit card fees, bank fees and cable contracts. In each case, customers are spending a lot of money year after year. "These companies don't want to lose you."

For example, if you get hit with a $37 late fee one month on a credit card, call the credit card company, remind them of how long you have been a customer and ask them to waive the fee, he advises. You might be surprised at how successful you are.

Negotiating a fee or contract doesn't mean you need to be nasty or rude. In fact, there's no reason to approach bargaining that way.

"I also want to point out that this isn't adversarial, whether you're negotiating fees or you're negotiating a salary," says Sethi. "You can actually do it very politely and you can both be on the same page.

"You don't have to go in there and sock somebody in the face and crush them. You can actually have a win-win for both sides."

Sethi offers detailed case-by-case negotiation scenarios on his website. And like anything else, the more you try it, the better you will get.