Sometimes I keep getting the same numbers on my new and first polyhedral dice and it feels like I'm doing something wrong.
You are almost certainly seeing a pattern where there isn't one.
People are hardwired to spot patterns, and are really quite good at doing so. However, this can easily lead to superstitions when things recur due to random chance.
One of my favorite statistics tricks is that you can tell with high certainty whether a person or a fair coin generated a list of 200 (or so) coinflip results. If there is no sequence of six heads or six tails in a row, it is very unlikely that it was actually generated by chance. People tend to see that as too much of a pattern though, and will avoid long sequences when trying to imitate randomness.
If you're at all suspicious that the dice aren't behaving randomly, use a dice cup. Drop the dice in the cup, shake the cup, then pour them out of the cup.
Cheaper dice may not be "as random" as higher quality dice. I've seen some that were misshapen enough to see it. But I've never had one that I could reliably say was rolling consistently high or low over a long time.
Seasoned gamers know to not just palm the dice and drop them straight down. Six-sided especially may not roll at all if you do that. Palm the die, shake it so it rattles in your hand, and drop it so it rolls after it falls.
Also, many gaming groups set up rules for dice rolling, with elements like:
- if it rolls off the table, the roll is void; reroll.
- if it lands on an edge so 2 or more sides are up, the roll is void; reroll.
- You can't roll the die and THEN declare what or if you act. Declare the action, then dice, then the results of the action attempt.
- no rolling ahead of time, as sneaky PCs might sit there, rolling dice until they get a perfect roll and then stop until it's their turn.
- if the cat steals the die before anyone reads the number, it's void; reroll sigh
Your mileage may vary, but I've seen rules like those.