[colinc]

This is my first year at growing vegetables, I dug over some weedy rough ground and created 2 13ft by 4ft beds in these beds I have grown early potatoes beetroots carrot’s Spanish onions lettuces and leeks, all the mentioned have grown really well. My question is I will turning my beds in to raised beds with scaffold boards and creating 2 more beds of the same size what do I need to add to soil to improve it even more.       

[Fisherman]

A lot depends on your type of soil but generally worth adding a combination of organic matter  / well rotted manure / coarse sand and leave it to over winter and breakdown. Take into account what your growing as some veg don't need manure and would cause growing problems (carrots, parsnips) while some need it (potatoes). Worth doing some research on crop rotation which there is a good section on this site, somewhere!

[Yorkie]

As Fisherman said, organic matter will improve all soil types - but avoid where you want to grow carrots & parsnips.

I wouldn't add sand unless you know the soil type needs it.