Home canning is easy enough to do.
If you are just starting out, here's a little information to help.
1. Measure headspace from the very top of the jar down to the top of the food.
Having the right amount of headspace is very important. Too much headspace and the jars may not seal properly. Too little, and your food could expand to the point that it leaks out, preventing a seal.
Once you are canning for a while, you will get the hang of it visually. You can also use your finger, I know that from the tip of my forefinger to the bottom of the nail is 1/2". No ruler needed.
2. Be sure everything is clean.
Perhaps this goes without saying. Wash everything before you start, from the food to the jars and lids.
Be sure the cat won't be jumping up on the counter, and don't let anyone lick the spoon until you are done.
3. In the beginning at least, don't change the recipe.
You can water bath process whole tomatoes, but if you go and start adding things like celery to make stewed tomatoes, you will need to pressure can.
High acid foods such as tomatoes and pickles have the acid in them to help preserve the food. The same is true for high sugar foods like jams and some juices. When you add other ingredients, you change that acid or sugar level.
While it doesn't hurt to add a little spice, otherwise stick to the recipes.
Likewise, stick closely to the processing times.
4. After the jars seal, should you leave the rings on or take them off?
There is a lot of bizarre misinformation out there, like 'if you leave the rings on, bacteria can grow under the ring and get into your food'.
Whether you leave them on or not is optional. We remove them for 2 simple reasons:
A. We are cheap and do not want to invest in a ton of rings.
B. You should take them off to wipe the jars anyway, especially if you pressure canned as there is likely some residue on the outside of the jars. May as well leave them off.
5. Label and date your food.
Is that salsa or stewed tomatoes? Hmmm....
Don't leave it to your memory. Just use a Sharpie marker to write on the lids, you'll be throwing them out anyway.
Be sure to add the month and year, to make rotating your supply easier.
Preserving food really isn't difficult.
Here's a short video to show you more.