The first challenge in starting tomato plants from seed is to choose which variety of tomato to grow. Here's a quick guide to the different basic types of tomatoes.
The most common type of tomato is called (fittingly enough) a standard or slicing tomato. These are the tomatoes that you generally find in the supermarket. Standard tomatoes are a pretty good all-purpose tomato and can be used for just about anything. If you're not growing many tomato plants and will use tomatoes in everything from cooking to slicing onto sandwiches to just eating them off of the vine, then standard tomatoes might be the best fit for you.
If you love a big, tender tomato, then consider Beefsteak tomatoes. These are the giant tomatoes that are often perfectly sized to slice onto a burger or sandwich. Some varieties can grow up to two pounds, so they're also great for stuffing and baking. Despite their great flavor, supermarkets generally don't carry beefsteak tomatoes because their tenderness makes them difficult to transport. This is no impediment to growing them in your garden, though.
Cherry tomatoes are, as you might guess, small tomatoes, usually growing no larger than a golf ball. You'll often find these in salads in restaurants because they add a great deal of flavor without needing to be sliced, and are easy for customers to pluck out if they prefer their salads without tomatoes. They're great as a quick snack, as they don't require preparation and are easy to pack and carry for a picnic or to take to work. As an added bonus for the tomato gardener, cherry tomato plants are generally very productive, yielding a lot of fruit from a small area in your garden.
Paste or plum tomatoes are generally used for canning and sauces. They have no core and a much lower water content, so they cook and stew beautifully. They also tend to have far fewer seeds. They are usually on the smaller side and more pear-shaped than most other varieties of tomato. Roma tomatoes are a popular type of paste tomato.
There are a few other considerations that you might want to take into account. Heirloom tomatoes are bred from varieties which have been in existence for at least three generations, and these are very popular with many gardeners concerned with maintaining the integrity of plant stock. You might also want to consider certified organic seeds, which have been bred and prepared using only organic methods.
No matter which type of tomato you choose, it is important when finding seeds to choose a reputable source. This is the best way to ensure that you get fresh seeds with high germination rates, as well as making sure to get just the type and quality of tomato plant that you're looking for. Once you've chosen and purchased your seeds, you're ready to start your tomato seeds.