Most witches include at least one central altar in a sacred space. Some witches believe it's important to place their altars in the east, where the sun rises. For practical purposes, placing the altar in the middle of your circle makes more sense, especially if a number of people will participate in rituals in your circle.
The altar provides a central focal point during spells and rituals. You can also display and store your magick tools here. You might consider decorating your altar with candles in attractive candleholders, flowers, statues of deities you feel close to, and crystals. Some witches like to leave their magick tools out on their altars at all times; others prefer to stash them away when not in use.
If you choose to leave your ritual tools out on your altar, be sure to display all four principal items — athame, pentagram, chalice, and wand — together to establish balance. These four implements represent the four elements: air, earth, water, and fire respectively.
In addition to the four primary tools, you'll probably want to keep a variety of other magick items and ingredients on hand for your workings. Most witches store a supply of candles in different colors, along with incense, essential oils, herbs, crystals, and gemstones. In time, you might also consider adding ribbons, parchment, mojo bags, a crystal ball, bells, a cauldron, tarot cards, runes, pendulum, ritual clothing and jewelry, and a grimoire for recording your spells.
Some witches change the decorations on their altars to coincide with the seasons and sabbats. This practice keeps your altar looking fresh and attractive, while also linking you with the Wheel of the Year and the cycles of life.