You will need open, friable soil though you can use a clay soil provided it is elevated and is well drained. I like to put rocks or logs around the edge of the proposed bed and build up the soil behind these, to create good drainage. Select ferns from a climate similar to your own. Natives of Victoria, Tasmania and New South Wales are quite suitable for our climate, as are those from cool climate countries such as South Africa, New 7ealand and South America. Hopefully this information will be on the plant label but if it's not, have a browse through fern reference books at your local library. - or better still, join the Society and gain access to our impressive lending library.
Ferns are all surface rooted.
Even the largest tree fern has a mat of roots near the soil's surface, not a tap root. This means they all need to be mulched with an organic material which will break down. Redgum chips and pinebark should only be used when they are very old. Think of the way leaf litter in damp forests falls continually, maintaining a thick mulch that is old and well broken down near the soil with the fresh material on top. The old material releases nutrients as it disintegrates and ferns are found growing in this rich medium.