I'll give the first answer too.
There are many ways. The right way is the one that works best for you. It can also vary based on the cut of tobacco you will be smoking.
Here's a video with some info.
I did also see a video about a week ago where the guy (some ole English chap) held the tobacco in his palm and twisted the upside pipe around it. Filled the pipe up nicely. Anyone know what that technic is called?
I really wish the man would make more videos. With his English accent and his smooth presentation he really makes a great narrative video. This was one of the first vids I found about packing a pipe and the method sails me through most loads.
I just prefer the old gravity fill method. I tend to pack a little loose at first and then tamp with my finger until the pack is at the correct density. I usually check density by taking a few draws before I light. Some guys say they like the resistance to be similar to sucking soda through a straw, but I like my draw to be a little more free than that.