Hi Fouzia

Perhaps start by digging all the literature from when the family was first described. This will help you to see the trend on characters that were studied before. It is a tiring exercise but its worth. One of the earliest taxonomic treatments I know of in the Malvaceae is that in Flora of Tropical Africa 1868, easily accessible on Biodiversity Heritage Library.

There is no fast method to do a revision of any taxonomic group. It is indeed a good start to search for literature and review the characters used, as it is a good start for almost any scientific project. Then, for a scientific revision of the group, you need to know the diversity of the group. The best (traditional) way is to do a large search for herbarium specimen. Since in the current time a thorough analysis of diversity on the DNA level is necessary, a good revision is teamwork. A good knowledge of basic taxonomy is necessary, access to herbaria and a molecular biologist are also necessary. Visits to the main regions of its distribution are unavoidable for collecting plants yourself. If the chosen genus has a pantropical or other global distribution area, take ten to twenty years to finish.