Chicago is in the USDA Zone 6a, which means that the growing season is generally from late April until early October. But don’t wait until the last week of April to begin! To ensure the longest growing season, you’ll need to start in March. Check your seed packets to determine exactly when to plant each vegetable.

The basic requirements for any seed starting are time, light, a growing medium, cleanliness, water, and attention.

Time is critical. Some species need weeks longer than others. Impatiens, for example, need to be started three months before the last frost date in mid- to late May; tomatoes need just six to eight weeks indoors. Use the seed packet information to lay out your timeline. You'll need to know the average frost date for your area—as early as the first week of May near Lake Michigan, as much as a months later in far western suburbs. That's when you can plan on hardening off most transplants to prepare to plant them in the garden.

Light can come from a sunny window if you are only starting a handful of seeds. Larger numbers will require artificial lights. They need not be fancy or expensive, though; a couple of standard fluorescent tubes in a utilitarian shop light works fine, if the fixture is hung on chains with S-hooks so its height can be adjusted. Install it securely in an out-of-traffic spot so the light can hang about 4 inches above the surface of your pots and can be raised as the plants grow. A lamp timer can turn the lights on and off; they will need to be on about 16 hours a day.

The growing medium anchors the seedlings' roots and holds water for them. But it must be porous enough to drain very well and allow the delicate roots to find their way between its particles. Potting mix is generally too dense; it's better to buy a sterile seed-starting mix.

The mix must be sterile because cleanliness is crucial: New seedlings are very vulnerable to disease. The containers, too, should be sterilized by dipping in a solution of 1 part bleach to 10 parts water. As long as it's clean, though, you can start seeds in anything that will hold a cup or two of soil — cell packs from last year, yogurt cups with holes poked in the bottom or special seed-starting flats.

Water is essential for the whole life of any plant. The mix should be moist when you fill the containers and sow the seeds. Mist the surface of the mix gently with a spray bottle and cover the containers with a plastic dome or tent them with a plastic bag to hold in humidity until the seeds germinate. Set the containers in a warm place, such as on top of the refrigerator or above (not touching) a radiator. Peek daily, and when you see green sprouts, remove the cover so the plants are open to the air and place them under lights or in the sun.

Like small children, seedlings demand daily attention. Read the packet directions carefully to learn how deep to plant the seeds and whether they need light to germinate. You'll want to label the containers precisely, with variety name and the date you sowed. Since seedlings can quickly dry out and die, check often to keep the mix evenly moist but never sopping (bottom-watering often works best). A few weeks after starting, give the seedlings one application of a very weak solution of all-purpose fertilizer. Don't overdo it.