Tomato Types: There are two types of tomatoes. Determinates and Indeterminates. I'll make this simple. Determinates are better for containers and small space gardening. They tend to fruit earlier and are a more compact bushy plant. The Indeterminates are a later producing variety and vine out a lot more. They most definitely need the support of stakes or cages. You can grow indeterminates in containers as well, you'll just have to support the plants with stakes or cages.
For first time gardeners I suggest buying transplants from the store....you can plant from seed if you insist, just know that those seeds will require grow lights, a heated seedling pad and babysitting for 2 months. There are many choices to pick from when you check out your nursery. Ask yourself about the space you have. If you're planting in the ground expect for 1 indeterminate tomato plant to have a height somewhere between 3-10 feet. They also need to be 3 feet apart. Now think about your uses....do you make sauce or salsa? If you do then you'll want to choose a variety like Roma or some hybrid "sauce" variety. If you use them for sandwiches.....think about Beefsteak, Supersteak, or Big Beef. If you use them in salads think about getting Cherry, Grape, Sweet 100, or Sweet Million. If you're a little more experienced then choose an heirloom seed to try. An heirloom is an "original" variety of tomato in which the seeds have been "passed down" from gardener to gardener over generations. They're great to grow, they do take a little extra work. Most of the tomato plants you'll buy from the store are not heirlooms. Hybrids will have more disease and bug tolerance than will an heirloom. Sometimes you can find an heirloom Brandywine tomato at the store....but generally you need to start those from seeds.
Now that you've decided on a type of tomato...how do you pick a good plant? I look for plants that are nice and green, no discoloration, and no speckles. I also don't buy plants that already have tomatoes on them. This is because when a tomato sits in a pot for too long (specifically the small nursery pots) they are forced to fruit early. Your plant won't get very large and will stop producing early. This has been my experience. So I look for plants that have not yet bloomed.
Once you have your plants or seedlings. If you have seedlings you've grown indoors, you must harden them off. Meaning they need to get some outside exposure to toughen them up a bit. This can be done by sitting the seedlings outside for a couple of hours a day (morning) and then brought back inside. Do this for 2 weeks. The transplants you buy from the store don't need to be hardened off. If you want earlier tomatoes, then buy some black or red plastic to put over the ground 2 weeks before you plant. This helps to preheat the soil....translating to earlier tomatoes.
Planting. Dig a hole in the ground or pot, then put some well rotted compost down at the bottom of the hole. Place the tomato plant in the hole and cover with soil. You should bury some of the stem in the ground...even almost up to the leaves is fine. The tomato can produce roots off the stem making it a stronger plant. Once the tomato is in the ground, stake it or cage it. Don't wait, its difficult to do once the plant is big, and you end up breaking vines trying to do so.
Watering. This is the most important part. You can even skate by if you neglect to fertilize regularly (don't ignore it altogether)....but don't forget to water them. Irregular watering can cause the tomato fruits to rot on one end, crack and split...or be misshapen. None of which are a good thing.
Bugs and worms. Ok....be on the lookout for Japanese beetles (ohio)....and tomato horn worms (everywhere). There are of course many other bugs that can attack your plant, these are the most common. If you have access to buy ladybugs and/or praying mantis pods from your nursery, do so! Ladybugs and praying mantis will eat damaging bugs. If you buy ladybugs....release them at dusk, they'll stay in your garden. If you release them during the heat of the day they will all fly away. Praying Mantis pods can be placed around your garden to hatch. If you leave the pod in the container you bought, they will hatch and eat each other and only one will remain living. I know its not a lovely thing to think about but that's what will happen! You have only one option when it comes to the tomato horn worm. These are large green worms that you'll have to pick off by hand (or use a stick....my preferred method) they will eat everything in site. Get rid of them!
Fertilize. You can buy Miracle Gro if you want to....they make a special tomato fertilizer. I prefer used coffee grinds. They're organic, free and work well for tomatoes, peppers, and a variety of flowers. Like roses and hydrangea. Save a coffee can, put your used grinds in it and stick it in the freezer. Use that to mulch your tomatoes with. It works very well! I usually fertilize every 2 weeks.
I think that's about it! If you follow these steps you should have plenty of tomatoes for you and probably your neighbors! Can't wait for March 15th! Get your seeds early!