The Wiccan Altar is a place of magick, prayer, ritual, and meditation. They can be made out of literally anything: A chest of drawers, a windowsill, a bookshelf, a small table, and so on. Some people may only have a temporary altar, set up just for rituals, but most people have a permanent altar of some kind. Altars are very personal things and may hold your thoughts, feelings and tastes in any way you choose. Some people like to keep their altars very simple; whereas others may have many items on theirs. Each altar is individual although many share similar characteristics:

Goddess and God figures:

Small statues, figures, pictures, or candles to represent the Goddess and God. If you're using candles then the Goddess candle is traditionally silver, white or green. The God candle can be red, yellow or gold. The Goddess candle should stand on the left of the altar, at the back, and the God to the right.
The tools of the Craft are associated with either the Goddess or the God, and should be put on the according side

Tools:

Cup, pentacle, bell, crystals, and cauldron - all associated with the Goddess and may be placed on the left of the altar. If your cauldron is too large then it can go on the floor to the left.
Tools associated with the God are: Censer, wand, athame and bolline. These should go to the right of the altar.
You may also want to have a small offering bowl or plate, an altar candle (when doing ritual/spellwork light this candle first then light all the other candles from it.), your Book of Shadows (often tho there isn't enough space so just keep it nearby), A wheel of the year (a round piece of card or a plate divided into eight sections - each section labelled with a Sabbat and decorated with appropriate colours and symbols)

Your altar might vary in appearance throughout the year.
In autumn you might decorate your altar with autumn leaves, acorns, horse chestnuts, crab apples. In spring it may be snowdrops and other spring flowers.
On Sabbats and Full Moons you may change the appearance of your altar to suit the particular festival or moon that is being celebrated.

A lot of people have altar cloths to go over their altar, it's not worth spending tons of money on an altar cloth because it'll be dripped on with wax, ripped and spilt on (although all of which add the 'rustic' feel!) Altar cloths can also change throughout the year; some like to have a different coloured altar cloths for each Sabbat or each season, but lets face it, we can't spend all our money on altar cloths. A lot of people only have one. You could sew a light colour fabric to a dark fabric and then flip it over depending on which half of the year it is (from Yule to Midsummer: light, from Midsummer to Samhain: dark). As I said before, don't fret about getting a really plush altar cloth, you can use a square of silk which you can find in accessories shops, they don't usually cost more than a fiver and there's usually loads of different colours. If you're feeling creative you could make your own and use fabric paint to draw symbols or runes onto it.

Altars needn't be just indoors. For some people it is far more convenient to have theirs outdoors. If you decide that this is what you want to do then choose a spot (not far from where you live) at the edge of a field, in a wood, by a stream, even in your garden. Make sure it is a place where you won't be easily disturbed. The great thing about an outdoor altar is that the trees and surrounding countryside create a wonderful ambience and the peace should help a lot in meditation. The only con is that during winter it may be virtually impossible to spend a long period of time with your altar, in which case you could set up a simple altar indoors.
Your outdoor altar will also be very simple. Pick up any items that you find lying on the ground that you think reflects the current season. Feathers, pebbles, and twigs will bring loads of great energy to your very personal, and natural, altar. The outdoor altar can be made from a large flat stone, a tree stump or just a flat piece of ground. Clear away any leaves or dead brambles. Use whatever you feel suitable for representing the Goddess and God. Unless it is a particularly still day it's usually very difficult to light candles unless you have them in a jar or a lantern of some sort. If you intend on doing rituals around your altar..take with you a rucksack with all the stuff you're going to need in it. Clear a circle on the ground..sweeping away any leaves or sticks. You could mark the edges of your circle with pale rocks, leaves, and flowers. But remember, when you've finished make sure you put back things as you found them and take any litter home!

Another way of making an altar, indoors or out, is to use a large sturdy stick or 'stang'. A stang can be permanent or just a temporary one that will be returned to nature when you've finished with it. Your stang can be propped up against anything, a permanent stang can be inscribed with meaningful symbols (never use a symbol if you don't know what it means!)..and can be decorated in any way you want: beads, feathers, buttons, ribbons etc. and should change depending on the season. A great thing about stangs is that they're very portable and can be easily moved when you want a change of scenery. Candles, offerings and tools can be placed on the ground at the foot of the stang.

If your parents don't know you're Wiccan it can be difficult to set up an altar that won't be noticed. The simplest altar may just be a shelf in a book case with a seashell to represent the Goddess and a pine cone or acorn to represent the God and a small wooden bowl for offerings of flowers, seeds, fruits etc. I remember one excuse I made was that my altar was actually a composition of items that I had to draw for an art lesson.