I'm getting into PLO8 myself. Biggest mistakes I have seen or read about are below. I am still learning myself so don't take the below as Gospel, its just what I have seen as mistakes so far.
1. Play hands and and stay in hands that you have a realistic shot at a scoop. I am not saying fold hands where you have a nut low draw but just saying scoops are very important.
2. Players are way too loose with their starting hands. If you dont have an ace in your hand you are at a huge disadvantage. Don't play the middle the cards such 6789 or hands of that nature. They dont have a lot of value in split pot games.
3. Dont raise or re-raise when you are chasing a low. If you have A2 in your hand and on the turn there are two 8 or lower cards which are not A2 you still have nothing and you are only looking at half the pot. Wait until you get that third board low card before getting aggressive.
4. Don't overplay a set. If you have KK23 and the flop is KJ9 you should bet as to not let others draw and you know there will no low but its still Omaha at the end of the day, Q10 is possibly out there along with flush draws so you have to be careful.