Apparently the plant prefers humus (high content vegetable matter, low content grit/sand), slightly acidic soil, - at least in preference to alkaline or chalky soil. This makes peat-based and / or ericaceous compost quite suitable.  Ericaceous soil favours acid loving plants, but to be honest, I haven't noticed any difference in results between using ericaceous and ordinary (pH neutral) multi-purpose compost.

I cook my soil in the microwave before using it.  I microwave a large bowlful on full-power (700W) for about 8-9 minutes.  I do this to ensure that larvae or bugs of any kind that might be lurking in the soil are well and truly killed.  If you are going to do the same make sure it's fully cooled down afterwards before using it.  

I mix the soil with about one third vermiculite. The theory is that it ensures the soil is well aerated and the roots therefore less liable to getting waterlogged and suffering root-rot. At the same time as preventing waterlog, vermiculite also holds moisture (and nutrients) and so ensures a good balance. 

Some people use perlite or a half-and-half perlite/vermiculte mix (again, one third mix to two thirds soil). This possibly favours soil aeration.  Personally, I swear by vermiculite.  It's slightly more expensive, but I had one plant potted with perlite in place of vermiculite and it didn't seem to do as well.  It could've been other factors, but perlite  just seems like a load of little polystyrene balls, - which do aerate, but at the expense of displacing nutritious soil when compared to vermiculite's ability to hold water and nutrients.

I put the vermiculite in the pot first then about another third compost, mixing up, potting and topping up with just compost. This way the vermiculite / soil mix is graduated, being more concentrated in terms of vermiculite at the bottom of the pot where water will settle.