Most manufacturers will recommend the use of a lining paper for a really professional job (normally 1000 gms). If your walls have previously been gloss-painted or covered with any oil-based paint or sealer it is a good idea to apply a lining paper to give a more absorbent surface for you wallcoverings to adhere to.
![lining paper](/content/images/blog/132494914084616404-lining-paper.jpg?w=1095&h=500&mode=crop&anchor=middlecenter&scale=both&quality=70&autorotate=true&format=jpg)