I have been gardening for 20 years, however I have never tried raised bed gardening and would like to set up raised beds for next spring. Could someone tell me how to go about building frames? Also.. I have really good soil in my garden, can I fill the beds with that soil or do I have to buy bags of potting soil? I need some one to clue me in as to what size of beds to build also. We live in the country and usually have a very large garden.