We do GRAMPS - Genre (is it a book, letter, poster, leaflet?), Register (formal, informal, neutral, mixed), Audience (children, customers) Mode (is the text spontaneous speech, planned speech or written text?) Purpose (to inform, persuade, advise, instruct) and Subject Matter (what the text is discussing).
I find this makes it easy to create different groups. Myteacher says always make a group based on something from GRAMPS (E.g. texts A,C and F are all texts to persuade), within this group you should write the similaritiesand differences of your texts. Never make a group based on a language feature;youβre really limiting yourself as to what you can write.