If you are starting tomatoes from seed it should say on the package. If you are buying starts it should say on the tag, if it doesn't you can look it up on the Internet by name. In my experience it used to always say indeterminate or determinant on the tag, but for some reason I noticed this year that information was lacking on a lot of the tags.
If you plan on canning, or freezing tomatoes and, or any of the things you can make with them determinate might be your best bet. They have a determined size, and for the most part produce most of the tomatoes all at the same time. This is why they say not to prune a determinate tomato, because you don't want to risk reducing your tomato production. Leave everything alone to get maximum amount of tomatoes.
For longevity an indeterminate tomato might be your best bet. Basically they are a vine and grow until the weather stops them. They produce a smaller amount of tomatoes at one time, but continue to produce them until the weather stops them. If you have enough of this kind of tomato you can do everything you can do with determinate tomatoes, you may just have to do smaller batches. The sky is the limit on pruning options for indeterminate tomatoes. Basically it comes down to personal preference and climate. If you live in a place like I do the options are wide open, because I have a very long growing season. I personally don't prune my tomatoes, except when it starts to bully it's neighbors, and then it's not strategic, but just removing the crowding branches. I get away with this because I live in a hot dry climate. Someone growing in a very humid climate would probably suffer fungal issues if they didn't prune. If you have a very short growing season, you may want to go with one of the more severe pruning techniques. This concentrates production, so you get tomatoes to grow size up and at least start to ripen before your growing window closes.
The great thing about growing your own garden is you get to do what you want. This is a blessing and a curse. Most of us like to do things our way, but if you're new to gardening, the options can be overwhelming. Single leader, double leader, let the plant grow but cut all the "suckers" off, don't prune.... it can be quite overwhelming. In this case talking to people who grow tomatoes in your area, find out what works for them (take what you learn with a grain of salt. Some people tend to believe if they have success growing a certain way everyone should too, and that's not always the case) If you have space maybe experiment with a few different techniques.
I used to only grow indeterminate. Now I grow both, because I have learned I can make the most amazing spaghetti sauce quick and easy with fresh tomatoes. I thought it took all day, and was difficult. Last year I threw a bunch of tomatoes ( all different kinds) into a pan with onions, garlic, and Basil. No blanching, or peeling, I just cooked it until the tomatoes were broken down, which is actually pretty quick, put it over pasta, and WOW it was better than anything jar sauce I even had. Quick easy probably a lot healthier, and taste so good. Unfortunately it was at the end of the season, but we did manage to freeze a couple of batches of sauce. In the future I would like to can some sauce, but for now I want to make and freeze sauce. Even the frozen sauce was way better than the jar.
Sorry this was so long. I hope it helps. Good luck