If you want to plant tomatoes, here's my advice: don't get too carried away! Unless you're feeding dozens of people, don't buy more than two plants. Yes, I know you'd like to try a green one, a yellow one and that old heirloom variety, that funny striped one and your favorite cherry type, but you'll be sorry if you buy them all. If they're indeterminate varieties (see below) you'll need to get out a machete just to walk by them in midsummer. By then you'll be drowning in tomatoes even if you harvest every day, and the over-ripe ones you miss will attract flies and skunks.
If you're a beginner you need to learn some important terminology before you buy your plants. First, indeterminate versus determinate. Indeterminate means the plant keeps branching and growing. They sprawl over the ground or try to climb up any support they can find. They get large and bear fruit over a long season In contrast, determinate tomatoes stop growing once the top flowers set fruit. Determinate tomatoes (also called bush tomatoes) are more compact and have a shorter season than indeterminate types.
The second thing to learn is disease resistance codes. These are single letters that should be on the label of plants in the nursery; they signify the diseases that a variety is resistant to. Letters are good - the more the better! Collect them all! Because, sad to say, tomatoes can get a lot of different diseases, some of which will kill a plant dead, early in the season, and you'll be left with no tomatoes! I won't bore you with the details of all those diseases, I'll just show you the standard list of good letters to look for. In my opinion, V and F are the most important. I consider them essential; the others a nice bonus.
V Verticillium Wilt F Fusarium Wilt FF Fusarium, races 1 and 2 FFF Fusarium, races 1, 2, and 3 N Nematodes A Alternaria T Tobacco Mosaic Virus St Stemphylium (Gray Leaf Spot) TSWV Tomato Spotted Wilt Virus
Now that you know a bit of the lingo, you're ready to go buy your plants. BTW, don't try to start from seeds. It's too late in the season, and you'll be happier with plants anyway. I always buy my tomatoes from Yamagami's Nursery. I'll let you decide which varieties to plant. My personal favorites are Sun Gold, Sweet 100, Sweet Million, Whopper and Black Krim.