Well ...without knowing what we're dealing with, below is a list of things to try. Before I put the laundry list down, I will always recommend that a long-term hobbyist invest in a level 1 UV sterilizer. It offers many benefits, including helping to clarify water.
- Purigen: it's magical in this area.
- Try some activated carbon. It's not for long-term use and will have virtually no benefit after about a week, but it's cheap and will help with certain haze issues. If you get Purigen, the AC may not be necessary.
- Coralife (coralifeproducts.com) - Pure-Flo 50 micron filter pads (placed in the filter). It will trap anything and, as a result, will clog quickly, but it is great at quickly polishing water.
Usually, in a healthy planted tank, clarity settles in after a few weeks and then it's nearly impossible to not have perfectly clear water.