I run a website teaching people how best to earn miles. These are the 7 worst mistakes I see consumers make with their credit cards.

• Dave Grossman is a miles expert and teaches people how to maximize their rewards points.
• Grossman believes many Americans neglect tips that can give them perks like flying first class.

This as-told-to essay is based on a conversation with Dave Grossman, who runs the website MilesTalk and teaches people how best to earn miles through credit cards and airline deals.

As an avid reward points collector and user, my "thing" is flying in First Class and staying in the world's finest hotels while barely having to pay anything.

I've spent years sharing tips for collecting miles and reward points through my websites, MilesTalk and YourBestCreditCards, which aim to help people choose what cards to use and how to use them.

If you're having dinner with me, I'm always going to judge what card you pay with. The US is one of the best countries where you can collect miles, but people just aren't maximizing benefits to the extent that I'd like to see.

Here are the seven worst credit card mistakes I see people make, but you can avoid.

1) Choosing a rewards credit card when they can't pay their balance in full each month

Rewards cards are great, but if you're going to carry a balance, they are your worst choice as they have the highest annual percentage rates (APR) of any card type.

If this is you, choose a card with a 0% APR intro or a Balance Transfer offer.

Get your balances down to zero, and promise yourself not to charge anything you can't pay in full. Then, you can get a rewards card.

2) Putting all of their charges on an airline or hotel-branded credit card

While those cards can come with great benefits, they're rarely your best choice for day-to-day spending.

You'll be tied to the whims of that one program, meaning you'll be stuck with whatever devaluations this one brand introduces.

Use a card that earns transferable points like American Express Membership Rewards or Chase Ultimate Rewards. That way, you can move your points to the airline or hotel program that will work best for each trip you're planning.

That basically makes you a free agent.

3) Forgetting to have at least one card that earns 2% back on everything

It's so easy to have a credit card with no annual fee that earns 2% back on every purchase, like the Citi Double Cash.

But most people only have one or two cards in their wallet, with the default on both clocking in at just 1%.

If you're buying something that isn't in a bonus category on one of your cards, then you should always be able to fall back on a default card that earns at least 2%.

4) Not putting in effort and wasting points on low-value redemptions

The best return you can get for your points is on the rewards that take some effort to understand.

While flying First Class on a flight to Asia that costs $20,000 or more might not have been on your list, you can often use rewards points to get a redemption using a transfer partner.

Here's the crazy part. You can do this for the same amount of points you're probably spending on $600 worth of gift cards.

For example, you could fly the world in business class, stopping up to 8 times, using just 125,000 to 145,000 Amex points with ANA as a transfer partner. But you'll have to do your research.

5) Cashing out on gift cards

This is often not a great way to use your points.

Most gift cards get you 1 cent per point in value, which isn't great, and sometimes you get even less than 1 cent.

Never accept less than one cent per point on a transferable rewards point. You can usually get these with Amex, Chase, Citi, or Capital One.

6) Cashing out rewards points at checkout

Amazon likes to ask you to spend your points at checkout. It could be your Amex points, Hilton points, or any other program, but the result is the same.

Cashing out at checkout often gets you even worse value than spending points on gift cards.

An Amex point, which I value at 1.7 cents when used with travel transfer partners, will give you just 0.7 cents a point when checking out at Amazon.

7) Neglecting bonus categories that match their spending

Make sure your biggest spending categories are something you are earning more than 2X points on.

If you spend a ton on groceries, you should have a card earning 4-6X on groceries.

If you spend a ton on dining, your earn rate should be 3-4X.

Many people earn only 1X points with their purchases, and they're leaving a ton of value on the table.