Alternate slices of tomatoes and mozzarella on a plate, overlapping them so you can see some of each of the slices - you might have the right amount to alternate every other one, but it doesn't matter. It depends upon the size and thickness of your slices of both the tomatoes and the mozzarella.
Stack up the basil leaves one on top of the other. Roll them up fairly tightly, then cut the rolled up leaves crosswise into thin slices, as thin as you like. Sprinkle those over the tomatoes and mozzarella.
Drizzle the olive oil over the top - don't be shy with it. Sprinkle with kosher salt and freshly ground pepper. If you like, sprinkle the plate lightly with the balsamic vinegar as well.
Notes
As for which kind of tomatoes to use? Red, yellow, orange, striped, smooth, lumpy, heirloom, all are fair game. If you live near a farmers market, there is that moment when the tables are piled high with all kinds of crazy looking tomatoes with funny names; Green Zebra, Brandywine, Lillian’s Yellow Heirloom, Mortgage Lifter, Black Crim, Purple Calabash, just to name a few. Grab them all.