A personal altar has several purposes, It dedicates a space to the things that are most important to you - a person, a goal, an ideal or focus in your life. It can add beauty to any space in your home; it provides a place to reflect on your personal or spiritual priorities. It fills a space with your unique, personal, creative and spiritual energy! It is a work that expresses your imagination and intuition.
Your altar may be large or small. A personal altar can be set up in a dedicated space where it is the center of focus for the room (such as a meditation room), it can be created outside in your garden, or it can be located in a small section of a room, such as a mantle top or a side table. No matter your religious beliefs, a personal altar will reflect your spirituality and give you a creative outlet to express your goals, beliefs, and ideals.
Your personal altar should have a theme. There are many types of personal altars. Use your imagination and your intuition to find a theme that expresses your intent. Here are only a few ideas for altar themes.
You can make an elemental altar that focuses on the four elements of nature - air, fire, water and earth. It is an ancient custom of many civilizations to pay homage to the elements. An elemental altar brings the power of these elements into your personal environment and brings you into harmony with the elements around you.
A meditation altar may contain crystals and gemstones chosen for their metaphysical properties to enhance your spiritual awakening. Read more about Meditation Altars here.
Goals or Crystal Grid Altar:
This would be an altar where you keep a crystal grid or a medicine wheel that has been charged and programmed for a specific goal you are working toward. Perhaps you want to make a love altar, or a protection altar, or an altar to generate money and good fortune. Read more about making a crystal grid here.
Ritual Altar is an altar where you perform any kind of ritual - for example; cleansing stones, programming stones, dedicating stones, etc. can all be done as a ritual. Here you would keep and store items used in the ritual. Magic rituals would almost always be done at an altar. Read about a magic rituals altar here.
This may have photos of loved ones that have passed on. Fresh flowers and personal mementos would pay homage to a life that you want to honor and remember. It may include a place for prayer and reflection. Get ideas for a remembrance altar here.
I like to create a new altar for each season as it arrives. This helps me to celebrate the season and decorate my home at the same time. For example, during the Spring I may display gemstone eggs (for rebirth and fertility) along with crystals or gemstones in oranges and yellows (for creativity). I will add fresh flowers and a lovely silk scarf in a pastel color to complete the arrangement.
Choosing a Location for Your Altar
In choosing a spot to make your altar, consider whether you want your altar to be your personal retreat or you want to show it off for the enjoyment of others.
If you will be displaying delicate items, ensure the space is well protected from pets and small children. If you don't want others handling the items on your altar, consider placing it in a cabinet where it will be protected by glass doors.
If you will be meditating or praying at the altar, you will need to create it in a quiet place where you will not be disturbed. There should be a space for a cushion or seat.
Create your altar in a place that is appropriate aesthetically - it can be used to enhance the beauty of any room by choosing colors and items that fit in with the theme of the room.
Decorating Your Altar:
Depending on your theme, 1 or 2 items should be featured on your altar with additional items around the main focus. Fresh flowers or plants, candles, incense, silk or cotton scarves, rose petals, decorative stands, gemstone bowls, photos, written notes or affirmations, soft lighting, trinket boxes, totem animals. the possibilities are endless.
Do create an altar with a central focus and keep it clean and uncluttered.
Change it when you achieve the goal or when your inspiration sparks a change. You can have as many altars as your space and imagination allows!
nice copy/paste of the article. while this article does provide some good points and more of a strict ridged set up of altars, please note unless you follow a path that absolutely need it a specific way, your altar can be set up however you feel works best. i change mine fairly often [every 6 weeks i think] it can have more or less items depending on various factors. my god and goddess statue can change from one side to the other, or even have them in the center of the altar. the candle is also moved around a lot  currently its in the front slightly off center] the offering dishes are always at the far back because if i offer any meat my cat tried to eat it, so i have to place it in such a way the cat either can't smell it, or if he gets to it, he has to land on my incense burner or something which screams 'hot and dangerous' [sounds cruel, but he doesn't jump up with those things in the way of his handing space, even if i'm not burning anything]
also, in regards to the altar having to be neat and tidy, no. personally i can't stand clutter, and unless i've got a lot of decorations on the altar for a sabbat, i only have about 5-6 times on it at all times, but i know people who can't stand empty space on an altar. one friend has an altar cloth [i don't have one] , there's candles everywhere [wax on the cloth] dishes, all her tools, statues, flowers, incense, it's covered. plus she never really cleans it because there's too much stuff, but its' constantly in use, not a day goes by she doesn't light a candle, or pray, or give an offering or cast a spell using the altar. it works for her and the idea of having a tidy space drives her crazy because she feels it's for display and not use. [meanwhile i'm the opposite, too much stuff would make me go insane] point is, read up on altars and how they are 'traditionally' set up, then do what makes you happy.