Among the new-to-LT block attribute tools in LT 2010 is the Block Attribute Manager. You can find it on the Attributes panel of the Insert tab as "Manage", or at the command line as BATTMAN. (And if you just started singing the theme song, you're not alone.)
The Block Attribute Manager helps control the order of your attributes so that you can enter data in a logical way. For example, this block has its attributes out of order -- I'd like to enter Line 1 first, then Line 2, and so on, but right now they're mixed up.
(Yes, this attribute editor is different from the one available in LT 2009 and earlier. No, I haven't posted about it yet...but I will soon.)
To fix this, I'll run BATTMAN.
The "Move Up" and "Move Down" buttons rearrange the attributes until they're in the order you want.
"Edit" launches the Edit Attribute dialog, where you can make changes to the attribute's overall properties, including its default value and prompt.
"Remove" deletes the attribute from the block definition.
"Sync" applies your changes to all block instances currently in the drawing.
You can use the pull-down at the top to switch between block definitions to make changes to the order of their attributes.
Along the bottom, "OK", "Cancel", and "Help" are pretty straightforward.
"Apply" saves your changes without closing the dialog so you can continue to manage attributes for that block or others.
"Settings" brings up a small dialog that has mostly to do with which properties are displayed in the main dialog window (like Tag and Prompt above). It helps you to distinguish between attributes, in case you have some with similar properties.
Two options you'll want to pay closer attention to are the ones circled in red. "Emphasize duplicate tags" shows you when you have two or more attributes in a block with the same tag. This is generally considered bad practice, because it can cause some unexpected behaviors.
"Apply changes to existing references" does exactly that -- if you uncheck the box, existing blocks aren't modified unless you use the Sync button in the main dialog.
Once I've finished my rearranging and closed the Block Attribute Manager, I can go back to my block and see the correct attribute order.