Probably caused by air getting into the fermentation process. If you are at the beginning of the process, add one campden tablet per gallon of liquid and the following day add a turbo yeast.
Probably caused by adding too much sugar. Make another batch with too little sugar and blend together or add a vigorously fermenting must.
Probably caused by not adding enough sugar. Sugar can be added to the wine immediately before serving, or sugar syrup can be added if the wine is being stored.
Probably caused by insufficient tannin being released from the fruit. Add a cup of tea! One tablespoon of strong tea per gallon of liquid.
Add a pinch of salt per gallon to darken insipid looking red wine.
Or 2 tablespoons of dried milk per gallon to lighten dark-looking white wine.
Probably caused by too much lactic acid. Add one campden tablet per gallon of liquid and stir vigorously.
Probably caused by over-heating. Move the liquid to a cool dry place for 2-3 weeks to see if it clears on its own. If not, either add finings (call for guidance on the type and the quantity) or add some good wine of the same variety to the mix.