In winter, raised beds are better drained. In autumn, they warm up earlier, in my area that can mean a crucial few weeks head start on the tomatoes, enough to put the first fruit on the table around Christmas.
Raised beds can be made by using soil from the garden paths, which would otherwise be not productive. This soil in thrown up onto the bed and formed. The paths can then be made up with sawdust, so that any germinating weeds will be easy to pull. They can also be used as a place to throw the hand pulled weeds, prunings and other accumulated organic wastes, which can be composted down in place or collected later and sent to the compost heap.
Raised beds can also me made from soil brought in for the purpose, but I find buying soil is generally fraught with problems, such as weed seeds or sticky clay.
Raised beds also provide a psychological reminder not to step on the soil in the growing area. For some reason the need to lift your foot an extra 6 or 10 centimetres is a powerful disincentive. Best that the beds remain in situ for some time, so that the benefits from not walking on soil and adequate drainage can accrue. Raised beds at their best are the ultimate in no dig gardening, developing an excellent soil structure.
Some people compost in the inter row and move the bed over onto the path area every year or two. I like to keep mine in the same place and let the soil continually improve.
As the soil improves you will find that maintaining the edges of the raised beds gets easier. The better-structured soil keeps its shape longer.
The beds can be mulched, or un-mulched, depending on the crop and the amount of sun which the soil needs at different times of the year. I have mulched beds for the tomatoes and other bush crops, and the potatoes, and un-mulched beds for lettuce, onions, carrots and herbs such as basil and parsley.
The Homi is a Korean tool sold in Australia by Gundaroo Tiller. It has many uses, but the curved surfaces are excellent for forming and maintaining the raised bed. Otherwise I find a wide mouthed shovel is a fine tool for creating the bed, and a mattock to loosen the soil if that is necessary. I finish the bed off with a simple garden rake.
Off course there is always the option to finish the beds with formed sides. Some growers use boards, or sleepers, or bricks. I avoid these most of the time, although I must say they can look very neat and orderly. The problem is mainly that they provide harbour for slugs and snails. The materials also cost money.
If I do make sides, I like them to be firmly in place. Otherwise they move when I am leaning over the beds, or when I knock them with the wheel barrow. If I make sides, I use metal stakes to hold the boards in place.
The beds should be narrow enough so that they can be tended easily from the sides without too much stressful leaning. They should be wide enough to permit sensible use of space. I like to mix the plants up a lot. I probably do use rows, because I can estimate quantities better in rows (I plan a garden for successional planting and food self sufficiency). But I do plant rows of basil under the tomatoes, or rows of different root crops alongside each other. I also interplant the slower growing solanums and brassica with faster growing spring onions, rocket, lambs ears, quick growing lettuce or radish.
Raised beds are the ideal solution to sloping sites. They can be formed like small terraces, higher at the front. They solve the problem of water running off, mulch sliding downhill and that unpleasant, unsteady feeling which you can get working on a slope.
I value my permanent raised beds as one of the simplest, easily achieved garden design features. I like everything I do to have more than one function. Raised beds certainly fulfil this requirement. Free drainage, early warming, protecting soil from walking on and keeping the garden beds narrow enough to tend easily from the path.