The first thing you need to decide is if you can have a permanent altar or if you will have to put it away each time. The kinds of things you use for your altar are very much up to your own personal taste and preferences. It's important that your altar be a reflection of your own spirituality.

The first item of a permanent altar is the table. Some people prefer round tables as they are easier to get around in the midst of a ritual circle. Others like a square table that fits easily into a corner when not in circle. I personally like having storage space under my table in the form of a cabinet or shelves so I can store some of my ritual items. Some people use a large wooden chest. They can store everything inside and then use the top of the chest as an altar when in use. Many think wood is the best medium for an altar since it's from the earth. But I think metal or stone work just as well. I personally wouldn't use plastic or some man-made material, but that's just me. Whatever you decide on it's a good practice to cleanse and consecrate it before use. Wiping it down with saltwater or smudging it with sage are quick ways to do this. Also, exposure to the sun or moon will work equally well.