Although tomatoes are often regarded by many backyard gardeners to be difficult to start from seed with positive results, the process is really not as difficult or demanding as many would believe.
Firstly, we need a good grade of tomato seed to work with. The seed should originate through a reputable grower or dealer and be clean of dirt, debris, and other foreign materials. It is very important that we choose the best seeds we have available if we would like to acheive the most favorable results. In this sense, we want to select those seeds which are the most perfect in their condition and shape. The seeds should not exhibit any irregular deformities (although such deformed seeds are often useful to experiment with for genetic reasons). In addition, the seeds should not display any signs of prior germination, let alone any damage from shipping. These types of seeds are not suitable for growing and should be discarded.
Secondly, we need a container in which to grow our seedlings. There are a wide range of assorted pots and seed starting kits on the market today. My preference leans towards a tray of small 2 inch pots in a series with a clear cover that is only wide enough to provide easy placement on a window sill or greenhouse bench. Any number of the dozens of brands on the market are suitable. Otherwise, using 2-inch pots from your last nursery purchase is completely adequate.

About Soil & Soil Additives:
Place into the pots, a good grade of soil. The type of soil you use is dependent on your situation. If you have good rich soil on your property, your own soil is completely adequate and likely best. If you use soil from your own property, be sure to sift it free of rocks, old roots, and other foreign materials before placing it into the pots. This small amount of extra work will save you some headaches and extra work in the future. Do NOT use composted soil to start your plants. Although compost is beneficial to mature seedlings and adult plants, compost will generally contain a quantity of seed, be it grass seed, or even other tomato seeds depending upon what sort of materials are being composted. If you lack quality soil on your property, commercial potting soil is adequate. If you are interested in growing your tomatoes strictly organically, be sure to avoid commercial potting soils that are treated with chemicals or that feature chemical fertilizers or additives.

It is always necessary to dress up your soil. Seedlings require a tremendous amount of nutrients and simple dirt or simple plain potting soil is not adequate for optimum results.
One of the best things to add to our starting soil is a good grade of manure, my personal preference leans towards the manure of Chickens which is superior to any other you can find AND superior to any commercial fertilizer, followed by the manure of Rabbits. Do NOT buy commercially packaged manure if you are growing organic plants. Commercially packaged manure is a by-product of commercial stock or poultry growers and 99% of all commercial Poultry, Beef, and Pork farmers feed their stock commercial feeds that contain growth hormones and various chemicals. For the best results, find a small backyard breeder of chickens, rabbits or whatever you choose and obtain your manure from them. Most backyard breeders will be glad to have someone take this manure off their hands for a very small price simply because there is so much of it produced that it can be overwhelming to them. In addition, in working with the backyard breeder for your manure needs, you can easily question your source about the types of feed (as well as feed and water additives) he gives to his stock. Ideally, manure from grain-fed stock who are kept healthy with natural products (such as vinegar, garlic, and mint teas) is the best choice. In regards to the state of the manure, let me just say that all manure is not alike. So-called “Green Manure” (that has not dried) is especially high in natural ammonia and is not safe for your plants. Chicken manure and that of other fowl have in the past, gained a lackluster reputation for killing young seedlings. Many gardeners believe that this is due to an extraordinarily high nitrogen content that is safe only in small amounts, which they believe will burn up their plants. This is simply a false idea. Chicken manure for example has a relatively low nitrogen content that is nearly incapable of burning the roots of any plant unless heaped on in tremendous amounts. The problem some gardeners have had with it is actually that fresh bird manure is extremely high in ammonia and this level of ammonia is dangerous to plants. Therefore, any type of bird manure should always be cured to the extent that it is dry. Ideally, the best chicken manure will form in small, thin pieces (once scraped from perches and nestboxes) and be of a whitish-gray coloration that is flaky to the touch. In addition, it will be absolutely scentless and thoroughly dried. Bird manure in this state is at it’s absolute best for use as a fertilizer and should be crushed to a fine powder and a reasonable quantity of it mixed into the starting soil.
Another useful additive to your soil is crushed eggshells. Adding crushed shells in a good quantity to your soil is a good organic method of adding extra calcium and other minerals to your soil. If you are short on eggshells, a good grade of natural bone meal will also help, as well as provide other nutrients for your plants. Another potential substitute is crushed oyster shell (available from any feed dealer for Poultry) which can be added in a small quantity to your soil, although it is a bit large.
Next, place your soil into your pots until it is level with the top. Then water the soil and let it stand overnight. This watering will not only dampen the soil but slightly compact it to disallow movement of the seed after the first watering.
Germination:
The following day, sow your seed into the pots to a depth of about 1/2 an inch and cover the seed gently. A toothpick is an ideal instrument to poke a small crevice into the soil for the seed. Be sure to mark your pots in such a way to identify each variety if you are sowing more than one variety. In addition, it is also wise to keep records of your seeds and plants by assigning each seed an ID number (ie. #001-Armenia). Record the date of sowing, germination, transplant, flowering, and production, as well as any notes on each and every plant. If you are serious about your tomatoes, these types of records will be of great aid to you in the future.
After 5 to 9 days (depending upon the variety) germination should yield small seedlings breaking through the surface. The seedlings will grow very rapidly with proper care. As time passes, be sure to cull any undesirable plants out of your containers such as those which are stunted or display any irregularities.
Transplanting:
Provided the weather and season permits, you should prepare to transplant your seedlings when they reach about six inches in height. Your garden area should be completely prepared ahead of time and be evenly tilled and free of debris and roots.
The seedlings should be spaced approximately one and a half feet apart in a straight line. If you are planting multiple varieties, try to space the varieties away from one another to avoid cross-pollination. Place other types of vegetables (such as peppers or eggplant) between them. Although this will not necessarily prevent cross-pollination 100% of the time, it does help. If you have the space, by all means, plant your varieties in separate groups at a distance from one another. Using obstructions such as buildings on your property to separate varieties is also advised.
If the plants are somewhat lanky as opposed to bushy, clip the lower branches away from the main stem with a pair of scissors and bury the plant to the point where the lowest remaining branches are 2 inches above the ground. This will not only encourage a more bush-like growth but will also yield a stronger root system as the plant will develop roots all the way along the buried main stem portion. This will insure that your plants have a strong start. My preference is to also side-dress each plant with a 2-inch by 4-inch sheet of dried chicken manure placed about 2 inches from the plant’s roots. As this strip of manure will break down over time, it will provide extra nutrients for the plant as it matures. Waste products (such as fish organs) or compost may also be used. Native Americans side-dressed their crops with small fish or fish organs.
Lastly, place a good cage around the tomato. You can make your own from a wide range of materials or purchase some commercially constructed ones, whichever you choose. Although many people like to stake their tomatoes, I have never found this better than just satisfactory, and always recommend using cages to protect and support plants.