Pouring hot water through your filter before adding your grounds will help give you a better tasting pour over.
Your paper filter is slightly absorbent, and a dry filter will absorb the first few drops of coffee that flow through it. These drops are full of some of the best flavors in your brew and most of coffee's natural oils. By wetting the filter before brewing you give all of those tasty drops a direct path into your cup.
Pre-wetting your filter also helps keep your coffee hot. How many times have you made a delicious cup of coffee only to have it cool off before you've finished drinking it? Pre-wetting your filter with hot water will help keep your coffee hotter a bit longer. Just don't forget to dump out that little bit of water before you start brewing!