lime

I only put lime down where I intend to grow brassicas and have found it most beneficial. I tend to dust the area with lime in Jan/Feb so that it is weathered in by the time I plant out in the spring. Other crops (eg potatoes) prefer a more acid soil (lime makes the soil a bit less acidic). If you live in an area where the ground rock is chalk or limestone, you probably won't need to lime at all.

Hope that helps 

Just as Aelf said but make sure you don't put manure on the bed at the same time.
Leave a coulple of months between them.