Marrying someone who was a chef for ten years has certainly made for a lot of surprises in the kitchen over the years. One of the first things that surprised me was how he diced tomatoes - it seemed like he was throwing the whole thing away! But he explained that by leaving out the guts (my word, not his) of the tomato, you don't have extra juice seeping into your recipe. He was dicing these Roma tomatoes for me for a bruschetta chicken recipe I was making (stay tuned next week), and you don't want a lot of juicy tomato innards in bruschetta. It also just looks better and neater, and you don't end up mashing tomato all over the place (more super-technical cooking lingo, courtesy of me).
First, quarter your tomatoes.