There are no rules honestly, the basics are to add soft, hard, and aged cheeses, 1-2 cured meats options, 2-3 kinds of bread/crackers, some seasonal fruit and-or dried fruits, pickled or marinated items like olives and pickles and you can add a touch of honey and jam for a sweetness!
You can also add some greens for color like rosemary or arugula.
Start by adding the big items (cheeses and bowls/ mini jars), then the cured meats and crackers/ bread, fill the spaces with fruits and nuts then finish it with some greens.
On this board: (this was the first time I make a cheese platter by the way)
1. Cheeses: manchego, parmesan, comte, roule, rouefort, and goat cheese
2. Smoked turkey slices and bresaola
3. Dried apricots, raisins, dried cranberries, grapes
4. Salted crackers and toasted bread
5. Raw almonds and walnuts, salted cashews and almonds
6. Olives and cornichon
7. Fig jam and honey
8. Rosemary
Source: healthyliciousbysara