I use at least three different styles depending on what they are for.
The simplest way, core them, slice them and dice them. (great for a salad bar or if you are making a rustic sauce, soup, or chili)
If you want a real nice brunoise then you have to just use the skins, discard everything else. (pico de gallo or a garnish in a consomme)
For tomato concasse style you have to blanche and shock, core and peel, remove seeds and pulp, and then dice. (for making traditional French sauces with tomatoes)
There are probably many other ways.