This is easiest using some kind of food chopper or a blender or food processor. I have a hand crank food processor from Tupperware that I use.
Peel the garlic cloves and add to the food chopper. Cut the stem off of the jalapeno(s), then slice length-wise. This is the step that controls the heat of your salsa. Using a spoon, scrape out the seeds and the white ribs of the pepper. Leaving in some seeds and/or parts of the ribs will increase the heat in your salsa. Cut the jalapeno into small-ish pieces and add to your food processor. Pulse for a minute or so, stopping when the jalapeno and the garlic are minced.
Peel and cut the onion into large chunks. Add to the food processor with the garlic and jalapeno. Pulse/chop until the onion is chopped (to a size you like) - you don't want your onion to be too big.
Take the onion/garlic/jalapeno out of the food processor and put in a bowl. Chop the tomato and add to the food processor. Chop/pulse until the tomato is chopped to roughly the same size pieces as the onion.
Add the tomato to the bowl with your onion/garlic/jalapeno. We're almost there! Chop your cilantro and add to the salsa. Roll the lime on the cutting board to loosen the juices, then cut in half. Squeeze the juice from half of the lime into the salsa. You may need the whole lime depending on how juicy it is. I estimate you need about a tablespoon of juice.
Gently stir your salsa to combine. Add some garlic salt, but take it easy, you don't want to over salt. Taste the salsa with one of your tortilla chips to see if you need more salt. Add garlic salt as needed. Chill in the refrigerator for an hour or so to allow the flavors to blend. It is even better the next day!