Tuntable set-up mistakes?

I have seen posts with advice on turntables for those who are considering entering "analogue heaven." Past posts have addressed the varying opinions of best table/arm/cartridge combos and phono stages. My biggest fear, (I would be in the sub $1500 range for stage and table,) is improper setup, (cartridge alignment, weight, etc.,) which would rob me of the best function of what I have. Could you please advise on how to do this properly? What would you say are the biggest and most common mistakes made? Thank you for your help. Charlie