Do take a look at this post about how to choose hot peppers, when making your decision, but if you are just starting out, we would recommend starting with jalapenos. Jalapenos will give your salsa a flavor similar to a lot of store-bought brands, and they can be anywhere from mild to spicy, depending on how much veining appears on the individual pepper.
Tear all the chiles into large pieces and toast them in a large dry skillet over medium heat until they change color a bit, about 2 minutes. Add the spices and continue to toast for 2 to 3 minutes until everything is fragrant. Remove from heat and carefully add about 1 cup of hot water to just cover the chiles. Turn the heat to low and simmer for about 15 minutes.
Sterilize the jars and lids in boiling water for at least 5 minutes. Pack the salsa into the hot, sterilized jars, filling the jars to within 1/4 inch of the top. Run a knife or a thin spatula around the insides of the jars after they have been filled to remove any air bubbles. Wipe the rims of the jars with a moist paper towel to remove any food residue. Top with lids, and screw on rings.
My first experience with canning salsa (around 17 years ago, I think), included recipes from the Ball Blue Book (one batch of each) and some “mild” Tam jalapeno peppers. Those “mild” peppers ate through two pairs of rubber gloves and filled the house with fumes so strong that I could hardly breathe and my husband started tearing immediately as he soon as he entered the house when he came from work. The salsa was thin and watery, strong on vinegar, and not too tasty. I gave up on home canned salsa for quite a few years – I couldn’t put myself through that again.
UPDATE 09/06/17: Lots of you have asked for a weight measure on the tomatoes. I’ve been canning this salsa the last few days and experimented weighing and measuring tomatoes. The result? Tomatoes are unpredictable! Meaning, the exact weight (that will yield the 10 cups drained needed in the recipe) is EXTREMELY variable depending on the type of tomato used.
Combine all ingredients except cumin, oregano, and cilantro in a large pot and bring to a boil, stirring frequently, then reduce heat and simmer for 10 minutes. Add spices and simmer for another 20 minutes, stirring occasionally. Ladle hot salsa into pint jars, leaving 1/2-inch headspace. Adjust lids and process in a boiling-water canner for 15 minutes at 0–1,000 feet elevation, 20 minutes at 1,001–6,000 feet, and 25 minutes above 6,000 feet.