THIS PAGE on the Modern Snuff website.
First of all, every technique for taking snuff involves sniffing the powdered tobacco into the front portions of you nose. This usually takes just a light sniff. If you snort the snuff, and pull it too deep into your nose, it will hit the back of your sinuses and throat and cause a very unpleasant burning feeling and sometimes an unpleasent "drip" in your throat. Pulling the snuff in too deeply will burn, cause coughing, watering eyes, and just an all-around unpleasant experience.
It can take some practice to know how hard to sniff. So, start with the lightest sniff that still pulls the snuff into your nose, and work your way up from there. It is a lot easier to start with the lightest sniff and slowing increase how hard you draw the snuff into your nose. Very fine snuffs go into your nose with the lightest sniff, while courser snuffs take a little more drawing power with your sniff. When in doubt, sniff lightly.
Modern Snuff Website