Most beginner mistakes with points and miles do not come from picking the wrong card. They come from one specific habit: redeeming for the easiest option instead of the best one.
Here is what that looks like in practice. Someone earns a solid pile of points, opens their card's rewards portal, and sees an option to use those points directly toward a flight or hotel booking, right there in the app. It looks simple, so they book it. What they usually do not realize is that the in-portal redemption rate is often the lowest-value way to use those same points. The exact same points, transferred to an airline or hotel partner program and booked directly, can sometimes be worth two or three times as much for the identical trip.
The mistake is not booking through the portal, sometimes that genuinely is the right call for convenience. The mistake is never checking whether a better option exists first. A five-minute comparison, checking the portal price against a transfer-partner price for the same flight or stay, is often the single highest-value habit a beginner can build.
The second most common mistake sits right next to this one: letting points expire or sit unused for so long that the account closes them out. Points are not meant to be hoarded indefinitely. If you have a trip on the horizon, even a rough one, it is worth checking your balance and thinking about redemption options months ahead, not scrambling the week before.
Neither of these mistakes is really about being bad with money. They are about not knowing the system had more than one path. Once you know to check both, the easiest option and the better one, that single habit tends to close most of the gap between a beginner and someone who has been doing this for years.