http://www.carnivorousplants.org/seedbank/species/Sarracenia.htm
Scroll down to the picture "Sarracenia seeds over a 1 mm ruler".
Only a few insects are good pollinators for Sarracenia.
I think bumblebees are the best pollinators.
So if no bumblebees are flying in your garden during flowering time or if you keep your Sarracenia in a greenhouse, you need to hand-pollinate your plants. If you are not sure where to put the pollen, look on the same page at the picture "Female Flower Parts" and transfer the pollen to the "stigma".
BTW: Even with hand pollination you will perhaps get much less seeds per capsule than you can see in the picture of Fred Ps posting.