Starting seeds indoors is one of the best parts of gardening. You get to work with plants long before spring, and there is nothing more satisfying that watching seedlings push their way out of the soil.
Indoor seed starting isn't difficult at all, but you do have to take the time to prepare your seed-starting area. It doesn't really matter where you start your seeds as long as you can provide these basic conditions:
1. Heat. Nearly all vegetable seeds germinate best at 70 F / 21 C or warmer. That's true even of cool-weather vegetables such as broccoli and lettuce. If your air temperature is lower, invest in a seedling heat mat. With the gentle bottom heat provided by a heat mat, seeds germinate quickly and grow fast, which gives them a head start against seedling diseases.
2. Light. Once the seeds germinate, they need to be placed in strong light immediately or they will get tall and weak. If you have a greenhouse or cold frame in full sun, or even a south-facing windowsill, that's all you need. If you are using your basement or another darker space, invest in a grow light. Put the seedlings under it as soon as they emerge, and keep it just a few inches above the tops of the plants as they grow.
3. Containers. Anything can be a seedling tray, from a professional 20-row seedling flat to a recycled rotisserie chicken container. Just be sure it has drainage and isn't too deep -- you need only an inch or two of growing mix to germinate seeds if you plan to transplant as soon as they get their first true leaves. You should cover the tray with a plastic dome or even plastic wrap until the seeds are up, then make sure they have good air circulation to prevent disease.
4. Growing mix. Look for a product labeled seedling mix, which will be very fine and light with good drainage. Seeds have their own nutrients for germination so you don't need fertilizer in the mix until you transplant them to a larger pot. Sterile seedling mixes also are less likely to harbor pathogens.
The photo above shows a basement seed-starting station. 20-row seedling trays are placed under grow lights as soon as the seeds germinate.