Hoover just asked me for salsa-making advice, and my TL;DR version would be this: Don’t get fancy. You don’t know better than Mexican grandmas.
But the long version: Yes. Get all the seedy flesh out of the tomatoes, or your salsa will be a drink. And add the salt last, because it draws even more moisture out of the remaining skins. You want it as dry as possible, because it’s going to be juicy no matter what. Now granted, I don’t puree my salsa, I like to make it chunkier (even though that slurry stuff is fantastic, too), so it may be a simple case of a fine strainer if you’re going for more what you get at Chevy’s. Me, I like the pico de gallo style.
I also like to do my own chopping, and leave as little as possible to the blender, which is backed up by a Mexican grandma (see, I told you) in an article I was reading recently.
I stopped using garlic. It overpowers the salsa and doesn’t aid it. In my mind now, if you add garlic, you’ve just made bruschetta (which is why I used to think balsamic vinaigrette was a good addition). I also stopped using it in my guacamole, and the difference there is gigantic. Suddenly, you can taste all the creamy, buttery goodness of the avocados. I love garlic ‘most anymore, but man, it does not belong in guacamole. It completely razes the flavor of the avocado.
I do better when I stick to basics: tomato, onion, cilantro, lime juice, sallt, pepper, a little oil, some parsley. I used to throw in a lone splash of balsamic vinaigrette and soy sauce to be weird, but I don’t taste a difference either way.
It gets better after it’s sat half a day to a day, so make it early.