Whatever course you choose -- I would suggest making your bed no wider than 3-4 feet in one direction. This is so you can reach into the bed and tend to the plants in the middle without having to bend over really far or even step into the bed to keep your balance.
I just scraped off the grass, went to Home Depot, bought lumber, screwed it together with L-brackets in the corners, and filled it with dirt. I did not weed barrier.
I made my raised beds out of dirt. Its cheap and it doesn't rot. Looks pretty good too.
Used a variation of French Double Dug Raised beds. Made them about 3 feet wide rather than 5 or 6 as the instructions below call for. Also make them a little higher...just over two feet. Cut them into the lawn and a narrow (6"or so) trench filled with mulch along the border stops the grass from growing into the beds.
It all depends where you live. Hilling up soil and making raised beds without stone/wood sides is fine if you don't live somewhere that gets torrential monsoon rains like we do in Houston. In PA, you might be able to just do raised beds without sides. 4x8 is a good manageable size. I put 6-7 tomato plants in one of those.
Hadn't thought of that Feldon. Good point. We get pitter-patter rain here in CT mostly. Now and then a driving rain but every spot in my dirt beds not shaded by vegetables is covered with purslane which prevents erosion.
(that happened by itself. birds must have carried it in as I see it nowhere else in the neighborhood. Makes a nice living mulch for tomatoes, peppers and eggplant. Creeps within a foot or so of the plants and then stops.)
I recently purchase raised beds from Bluegrass Garden Beds and Raised Bed Garden Kits. They are different but I really like both. Raised Bed ships really fast. They are very easy to assemble. No tools required.
We purchased the lumber from Lowes. We have five beds 25' x 4' the boards are 6" wide. There's bamboo growing in the corner of our lot, so hubby cut some for stakes to keep the sides upright. Longer bamboo stakes are used for the tomatoes.
After gardening for years using raised beds I wouldn't garden any other way now. It started out of necessity because of very sandy soil and gophers. We had the lumber yard pre-cut redwood to the length and width of the
beds we wanted to build. The only other tool we needed for assembly was a drill and very large decking
screws. I used a 4 inch length. The beds were made of 2' X 12" redwood with 2"X4" corner pieces. I attached
aviary wire to the bottom of the beds for gopher control. Some of the beds lasted close to 20 years plus before the
termites hollowed them out. We have replaced those beds with new ones but still are using some of the original
beds. It was years later that I came along and cut capping for the beds from 2"X4" redwood. I used a mitre saw
for that. It gives the beds a nice finished appearance plus it gives you a place to perch if you are weeding.
I've wondered about using some of the new decking material that is being advertised but am not sure how safe
it is to use around food production. I try to garden as organically as possible so treated wood of any kind is not
used in the garden.
I love the raised beds because you can amend your beds generally or specifically for the crop you are growing. I
use a lot of compost in my beds and after all this time they finally resemble a nice loam.