As with most high-low split games you want to have been dealt a hand that gives multiple possibilities of winning so combining elements of good starting low and high hands gives you the best shot.
For high having one or two high pair is a decent start. (In 4 cards you will be dealt 2 pair about 3% of the time and a single pair about 30%) You have a small possibility of getting a full house, but most of the time trips is the best you'll get so the higher your pair(s) the better.
Several connected cards will be helpful for straights and a straight is often the best possible hand. Flushes require that all 3 cards of one side be suited and that does not occur often. Thus suited cards, though better than unsuited, are only marginally more valuable. Trips in your hand are worthless since you can only use 2 of your hole cards.
For low 2A is the best start. 3A or 32 gives you a one card draw to the nuts and either is absolutely playable. Unfortunately, when you have only 2 low cards in your hand there is a pretty good possibility that one of them will appear on the board and may counterfeit your low. For that reason a protected low like 32A or 42A is a far better hand. Whenever you hold one of these low hands with an ace you'd prefer the ace to be suited to one of your other cards.