It's a myth that you have to bend less with raised beds. The edges catch your knees so you have to bend and stretch just as much, or I do.
As well as all the stuff you want in the veg patch itself, there are other more general points to consider:
Aspect - does your slope face N,S,E or W? Best of course is south facing, but least good is north facing. Long beds are best running N-S so the sun can get to both sides. The same with a polytunnel, although ours runs W - E to catch a through breeze, and the more shade-loving plants go on the north side, which gets sun in the summer anyway.
Frost - is it in a frost hollow, or can cold air drain downhill?
Shade - are there close overhanging trees - these will cause shade, especially as they grow, their roots will steal moisture and nutrients from your plot, and they will drop leaves all over your patch in Autumn (not so bad as of course you can use them to make leaf mould)
Soil - do you need to improve the soil before you start? Do you need to arrange water drainage? Will you be bringing in soil from elsewhere for the beds?
Local climate and weather - you can't change that much, but if you are in a very wet area, then a less sandy soil is best. If you are in a very cold area, you need to think more about frost protection.
Wind - a very windy site needs a windbreak of some sort. We began with a 2m high green mesh windbreak, while the hedge grew in, far enough away not to shade the beds, but close enough to slow the wind. It's amazing the difference in microclimate you can create with good thick wildlife hedges
