lava can be a bugger, it can set fire to you diagonally as well as if you fall in, and it's so often under something good (like diamonds)
I often dig all around diamonds, carefully removing everything dull, even under - you can drop sand or gravel into lava to get rid of it, or chuck water on - though that will result in obsidian (or cobble if thelava is flowing)
you can drop sand or gravel into lava to get rid of it
I didn't know that..! Should've thought that was the case, but never mind. Does that mean that if the lava is more than one square deep, you need to drop several squares of sand into it?