I grow all my highland and intermediate Nepenthes in pure sphagnum moss, and it works well for me. Other media can be used, and it will be influenced by what is readily available in your area. Sphagnum moss is very easy to get hold of where I am, so it's easiest for me. In some countries it's much harder, if not nigh impossible to obtain (or it is prohibitively expensive. Rob Cantley from Borneo Exotics has been using coir and coconut husks with great success.
The general rules for a good Nep mix are: it must be light and airy - Neps roots don't like pushing their way through "soil", they like something easier to penetrate. It must drain well - Neps don't like to be sitting in a soggy medium for extended periods, it rots their roots (so they're not at all like Sarracenia). It helps if the medium holds moisture, because they do like to be moist, and watering plants several times a day is a pain and a waste of water.
Cheers, Hamish