This is a game of draw poker in which nothing differs from any other game of draw poker except that the high and the low hands split the pot. In some high-low games, the ace can be treated as the low card in a low hand, but these games are rare and I will consider only the game in which the high hand is reckoned exactly as it would be in any other poker game and the lowest possible hand is 7-5-4-3-2 of different suits. Straights and flushes count and must be treated as high hands.
One error that a high-low player may make is to treat the perfect low hand (7-5-4-3-2) as unbeatable. Such a hand is not more infrequent than a high full house. At least once in the lifetime of the high-low player, he is likely to hold the perfect low when another player also holds the perfect low. If the other player is equally ignorant, they will raise and reraise each other indefinitely, while the high player simply rides along with a cinch. Eventually they will split half the pot, having put in closer to one-third of the pot each, and the "perfect" hand will have wound up with a net loss. I do not intend to imply that a player with a perfect low should not back it strongly, but after four or five raises he should become suspicious. At that point, even if he has another perfect low out against him, if he calls he probably will do no worse than break even.