Tips for beginners from a mildly-advanced beginner:
Take the time to understand the canning process. When you do your first pressure-canning recipe, which is necessary for all low-acid foods (tomato sauce recipes are high-acid and use simpler water bath canning), don't think its like making stew were you just start cooking, set a timer, and go mow the lawn. You really need to be watching the canner for the entire time, making sure you are at or above the target pressure for at least as long as the recipe requires. If the pressure goes below target, you pretty much need to start the process time over from zero or plan on storing your jars in the fridge until you use them. Canning when done right gets rid of botulinum bacteria (which are present everywhere) and other bacteria before they can propagate in the food. The nefarious thing about botulinum is that they are very hard to kill and a botched canning job just gets rid of their competition, leaving a perfect environment for them to thrive. And don't forget that botulism can be deadly, and is caused by toxins that the bacteria release, not the actual bacteria. So if you botch a canning job and just plan on cooking the hell out of the food after it sits on a shelf for a while, you might kill the bacteria, but the undetectable toxins will probably still be there.
So as a rough idea, if you are canning some meat or fish, you will be pressure canning. You will probably spend an hour sanitizing your jars and lids and prepping the meat. You will spend another half hour packing the meat, cleaning jar rims with vinegar, and getting the canner up to a boil and venting steam for the required time. Once venting is done, you probably have another 90 minutes of processing time, and this is when you have to watch that gauge and adjust your heat to keep above that target pressure. So set aside at least three hours if not longer.
Canning recipes should be tested by a University Extension or other USDA-approved resource. There are some valid gripes about USDA practices these days, but the science around canning is well-established.
Ball Blue Book is a great resource for trusted recipes, but there are many additions and they rotate the recipes periodically. So if you see an older edition at the used bookstore, you might want to grab it. Also, the recipes are a bit minimal so, again, it is important to understand the process of canning before you start.
DIY recipes: One of the shortcomings of canning is that using home equipment is just not suitable for many common ingredients. A lot of people home can brown bread and flour-thickened soups and do just fine. But are you willing to risk killing someone for the convenience? I'm not. Making your own recipes is not totally out of the question, but you should always use a trusted recipe for the starting point and you really need to understand the process and which ingredients do what to the recipe. If you aren't 100% sure, just follow an trusted recipe. Last year, I found a University Extension that had an online recipe generator where you could add ingredients and it would produce a safe recipe for it. I did not bookmark it and now I cannot seem to find it anywhere.
Lids: Throw old lids out. Old unused lids will probably work, but new ones are cheap. You worked hard to secure the food and prepare it, don't let a 25 cent lid ruin it or make you sick. Old unused lids can be used for refrigerated jars, but use new, fresh ones when canning. And always toss used lids from canned food. Bands are a little more forgiving, but they are cheap too, so throw any out that are corroded or bent.
Tools: Lots of canners available, some pretty pricey. I have a big Presto aluminum canner. I like it because it is cheap and works. I have replaced the gauge twice now, and the gauge is readily available and cheap. Jars and lids can be found in most supermarkets and hardware stores. The other main tools are a canning funnel, jar lifter and lid lifter. These are all cheap and make life easy.