Step one: Add food!
Step two: Add Heat!
All else is secondary.
There is also no big secret about seasoning a dutch oven or any cast iron for that matter and its care. Clean is the most important thing so don't worry about using soap and water or scouring pads, get it and keep it clean you won't hurt it making it clean. After it is clean and dry wipe it with just a little bit of veggie oil on a paper towel, you can heat it until it smokes or follow any of a thousand different methods as you see fit, but I will offer this bit of information. Turn the pot or pan or dutch oven upside down if you are going to try to season it all at one time or after every use. This will allow the excess oil to run out of the pot or pan or dutch oven instead of flowing to the bottom and making some kind of thick gooey spot on the inside of the pot.
The real deal is this, every time you use your cast iron a little bit of the oil turns to carbon and gradually seasons the pot. This will tend to happen faster on the sides and in areas where you don't tend to rub the stirring spoon or fork against all that much, because you actually scrape off that carbon in very small amounts before it has a chance to build up very much. As long as you cook with oil or animal fat the carbon will keep building up over time. If you happen to burn something that sticks to the pot and have to scrub to get it off, you wont hurt anything but your back and some of the seasoning. Scrub off the burnt food and wipe the pot with a thin film of oil and let the seasoning start to build up again. I store my cast iron upside down in the oven, the same place my parents did and the same place that most of the people that I remember did and do.
As far as tomatos and acidic foods go in cast iron? I have eaten more sloppy Joes and spaghatti sause out of cast iron than I can remember. Just try not to burn it in the pot when you cook it (As with all foods) And don't store foods in you cast iron (As with all foods) Again if you scrub off the seasoning, then recoat with oil and give it some time to work back, no biggie. It is a pot, not some magical mystical thing it is for cooking your food, keep it clean and if you can keep it full of good cooking!