In general, place the larger plants towards the back e.g. runner beans (if they are climbers) tomatoes (if they are tall varieties) and Broccoli unless they are mini ones.
The shorter crops such as lettuce, spring onions and carrots, should be planted towards the front of the border, not only so they don't have the sun obliterated by taller plants, but also because you will probably be harvesting them first anyway.
Sweetcorn tends to grow very tall however to get good pollination, they should be sown in blocks rather than in rows so position those in a position which won't allow their shadow to block the light and sun from the other crops.
Lastly, broccoli and cauliflower tend to take much longer before harvesting so if you want to make use of the space in between time, you can sow some of the spring onions or lettuce in between them.
www.recipes4us.co.uk has a complete section about growing many veggies which also states the plants' height and spread.
Hope this helps
