Two methods stick out in my memory.
One is that you read it entirely intuitively, looking at the other cards, feeling their vibes, and deciding for yourself if the energy of the card in question feels negative, blocked, or otherwise like a reversal. I don't use this method myself because there is no accountability - no way to prove how I came to a certain conclusion about the card.
The other method, which I find more reliable, for reading reversals in symmetrical pips is to look at the card or cards that precede it. If the numerical values ascend at the symmetrical pip, it would be read as upright. If the numerical values descend at the symmetrical pip, it would be read as reversed.
Take for example the Six of Coins. If the previous card is the Three of Cups, it would be read upright. If the previous card is the Eight of Sticks, it would be read as reversed.
I like this method for determining reversals in those pesky symmetrical pips a lot more than just intuiting the meaning. Somehow, it feels more solid...
Ultimately, each card embodies the positive, negative, and all shades in between, so one doesn't necessarily have to use reversals in order to get the message across. A positive side to a card's meaning will always come with a warning, which might be interpreted as "reversed."