About oregano: One of the most commonly used oreganos is Greek oregano. It can grow pretty tall (over two feet!), so make sure to snip often enough to encourage new growth (and, you know, so it doesn't take over your space). The plant can last years in your home if it's well-maintained. You can expect, on average, two to three years of life.
To start growing: Buy two small plants or one large one. This herb is difficult to grow from the seed, so skip that route. Transplant the plant(s) into one six-inch (diameter) clay pot. Plant it in a mixture of half potting soil, half cactus sand, and make sure the soil is the same level as what you bought the plant in. If you plant it too deep, it'll cause the stem to rot, and if you plant it too shallow, the exposed roots will be damaged. Do not water it until the top half inch of the soil is dry, and do not fertilize. Important: While this plant is safe to grow indoors, do not place it above the kitchen sink or in the bathroom, as the moisture may cause it to rot.
To use: As a rule of thumb, six inches is a good length to start snipping off the leaves for use in cooking. Most of the time when you buy oregano, it will already be a bigger plant and you can use it immediately (it should at least be the size of your hand). Clip from the top, which will help the plant create more branches. Use it for Italian dishes like pizza and pasta.