g'day,

which ever suits you really in the end they all end the same way a bed of humus basically.

the point is to use whatever material you have or can get locally cheaply.

len

Here is a link that might be useful: lens straw bale garden

It depends on where you are starting. In lawns, lasagna or hugelkultur or framed raised beds. With really crappy soil, framed raised beds. In a large tilled space, low mounded beds. In the dessert, sunken beds. In large established market garden with already excellent soil, lowered paths.

All of ours raised beds are double dug using a shovel first and then a garden fork for loosening the deep stuff. Our soil is hard, red clay so the beds may only be dug to 12" in some cases. Each bed is double dug a 2nd time (first time in spring, second in fall) and then it is dug no more. The beds are raised naturally through the digging process. Soil amendments, compost, green manures, and decaying plant matter are turned under the soil with the fork before each planting but never more that 4-6 inches. Setting up the beds this way is pretty tough and it is a slow process. We are very happy with the results. There is a lot of info on the web about double digging.

The primary reason for building raised beds is because your soil has drainage problems that may be too difficult to overcome otherwise. If you have a soil that already drains well building a raised bed can create even more problems.
However, how you build a raised bed depends on you and what you have or even how much money you want to spend. Buying construction material, lumber concrete blocks, etc. can be quite costly. Simply piling soil up works well although that can be subject to erosion unless the soil is always planted with something.
Unless you pay close attention to the soil you buy, in itself fairly expensive, you can end up with a soil that needs more work then what you all ready have. Look closely at any soil you buy to be sure it is what you want. Many people sem to think that what is sold as "topsoil" is loam, but there is not enough loam in the USA to supply everyone that thinks they are getting just that. The definition of "topsoil" is the top 4 to 6 inches of soil, so it may, or may not, be something worthwhile.
How much do you want to spend?
What materials are going to use?
How much work do you want to do?

Here is a link that might be useful: About raised beds

My large gardens were started in brush-covered wild land. I hired a tractor to bush-hog what he could and cleared the rest by hand. I built massive compost piles with all the material he cut down. I hired him again to come back with a chisel plow to tear out the roots. Once I had finished clearing that, I bought a used rototiller and started building garden areas separated by grass paths, and planted a large crop of potatoes. My second year, I started double digging the beds into 3' wide rows. The topsoil from the paths was sifted on top of the rows to form a nice stone-free seedbed. My raised beds were about 8" high. My third year I started deeply sifting my beds, removing the top foot of soil and sifting it back in. I now have about 4 acres of beds that are built this way. They are about 3" high, and are only tilled after a green manure crop.

Raised beds mean different things to different people. Using treated timber to raise the root level above the surface of the ground may be neat and tidy, but I prefer digging a pathway through the tilled garden about 8" deep and filling that pathway with straw or moldy hay.
The bed is raised, by the sides dropping and raised further by the 8" digging spread over the top of the planting area.
Next year the new raised beds are centered over the top of the previous pathway of rotted down straw or moldy hay.