This 28-year-old staff sergeant raised his credit score nearly 200 points by watching YouTube—here's his best advice

Have you made a major jump in your credit score and would like to share your personal journey? Email reporter Elizabeth Gravier at elizabeth.gravier@nbcuni.com if you're interested in being featured in Select's new "Credit Scores: Then and Now" series.

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Kadeem Roberts is 28 with a total of five cards and an excellent credit score. But that wasn't always the case.

Roberts, who went to college for two semesters and withdrew because of the high cost, was doing odd jobs before a sales job rewarded him with a good salary. While he was looking to buy his first car with his new salary, he soon learned that he couldn't qualify for a loan to do so because his score was around 604 at the time, Roberts recalls.

"That was the first time I really started realizing how important credit was," Roberts tells Select. He ended up using cash to buy a car from a friend and spent the next couple of months turning to YouTube to learn about credit. He would search things like, "how to build good credit," and find videos that covered the subject. This is when he began paying off all his debt, which included a little over $1,200 in student loans and a maxed-out credit card with a $1,000 limit. Slowly, he saw his credit score start to increase. 

At age 23, Roberts enrolled in the military and is still currently serving as a staff sergeant in security forces, stationed at Francis E. Warren Air Force Base near Cheyenne, Wyoming. He says he is also working on his bachelor's degree in business administration with a concentration in IT management.

When asked to pull his latest score for this story, Roberts' score by Equifax and TransUnion (two of the three main credit bureaus) calculated an excellent 797 using the VantageScore 3.0 model.

Below, Roberts, who recently authored a book called, "The Secret To Mastering Credit: A Beginner's Guide," shares his No. 1 advice to raising your credit and reveals the five cards he carries.

Roberts is big on appealing to the younger generation because he knows how much of a difference learning about credit early on can make. In his early days, he says he would charge a lot of day-to-day things and rely on credit to get by.

His No. 1 piece of advice in having good credit habits is this: get informed about the basics.

"The number one thing I would say is just try to understand at the basic level," Roberts says. "There's so much information floating around out there about what's good for credit, what's bad for credit — [just] understand the fundamentals. It doesn't matter if you're trying to build or repair [your credit], the fundamentals are always going to be the same."

These fundamentals, or rules of thumb, include paying your credit card bill on time and in full, as well as keeping a low credit utilization rate (the ratio of how much credit you use to how much you have available). Roberts also recommends understanding what your credit card company is reporting to the credit bureaus. And if you're like many and already have credit card debt, he recommends making an actionable plan to fix it over a specified time frame.

"I'm a big advocate for credit cards, even though I did have credit card debt," Roberts says. "It's just a matter of understanding how to use them properly."

Roberts no longer has student loans or credit card debt, and he is in the process of buying rental property. He has a debit card, though he says he can't remember the last time he used it. Much of his spending goes onto one of the five cards he carries.

"Pretty much any bill I can pay with a credit card, I pay with a credit card," Roberts says. For him, this includes charging his cell phone and Internet bills, as well as his car insurance. He pays rent with a check and makes sure to pay his card bills off on time and in full every month to maintain a high credit score. Note that you should avoid using a credit card when there are processing fees, which often run between 2% and 3%.

Of the five cards Roberts has, two are business cards that he uses for marketing his book. These cards help him separate his personal expenses from his advertising expenses. 

Here are all five cards he carries:

1. Prime Visa: Roberts' first ever credit card and the one he uses every day, the Prime Visa, is worth holding onto. It's his oldest card, and longevity of credit can be an important factor in calculating credit scores. The Prime Visa ranked on CNBC Select's overall list of the best rewards credit cards because of its perks for groceries, online shopping and streaming, as well as its generous sign-up bonus ($100 Amazon Gift Card instantly upon approval exclusively for Prime members). With his Amazon Prime membership, this card lets Roberts earn unlimited 5% cash back at Amazon.com, Amazon Fresh and Whole Foods Market, unlimited 2% back at gas stations, restaurants, and on local transit and commuting (including rideshare), gas stations and drugstores, 5% back on Chase Travel purchases, and 1% back on all other purchases.
2. Bank of America® Customized Cash Rewards credit card: The BoA Customized Cash Rewards card offers Roberts 3% and 2% cash back on his first $2,500 in combined choice category/grocery store/wholesale club purchases each quarter, then 1%.
3. Blue Cash Everyday® Card from American Express: Amex's Blue Cash Everyday Card ranked on CNBC Select's list of the best cash-back credit cards with no annual fee* because of its rewards on grocery purchases. With this popular card from Amex, cardholders like Roberts can earn 3% cash back at U.S. supermarkets (on up to $6,000 per year in purchases, then 1%), 3% cash back at U.S. gas stations, (on up to $6,000 in purchases per year, then 1%) and 1% back on other purchases. Cash back is received in the form of Reward Dollars that can be easily redeemed for statement credits. *(See rates and fees)
4. American Express® Business Gold Card: For those who have business expenses like Roberts has for marketing his new book, the Amex Business Gold Card lets you earn 4X Membership Rewards® points on the 2 categories where your business spends the most each billing cycle from 6 eligible categories. While your top 2 categories may change, you will earn 4X points on the first $150,000 in combined purchases from these categories each calendar year (then 1X thereafter). Only the top 2 categories each billing cycle will count towards the $150,000 cap. These categories can include expenses made on business travel like airfare, gas stations and eating out. For Roberts, this card comes in handy because of its advertising and shipping expense categories.

1. Bank of America® Business Advantage Travel Rewards World Mastercard® credit card: Another business card, this one lets Roberts earn unlimited points for his business purchases. The BoA Business Travel Rewards card offers an unlimited 1.5 points for every dollar you spend and an unlimited 3 points per every dollar when you book your travel (car, hotel, airline) through the Bank of America® Travel Center.

Roberts' next card? He has his eye on The Platinum Card® from American Express to help cover future travel costs.

For rates and fees for the Blue Cash Everyday, click here

For rates and fees of The Platinum Card® from American Express, click here.

Information about the Prime Visa, Bank of America® Customized Cash Rewards credit card, and Bank of America® Business Advantage Travel Rewards World Mastercard® credit card has been collected independently by CNBC and has not been reviewed or provided by the issuer of the card prior to publication. If you purchase something through Select links for the Prime Visa, we may earn a commission.