I use Murphys 'fining adjunct' and AllkleerA (isinglass).
You need sound brewing practice as outlined by others. CHill the beer as cold as you can get it....0-1 deg C is good, add finings adjunct and then leave for 48 hours. At this point I rack to keg and add the Allkleer (or Cellarbrite).....job done. You could also add the Allkleer to the fermenting bucket before kegging/bottling.
Get advice on making beer from raw ingredients (malt, hops, water and yeast)