change schema of installed db

Hi,

	We have a database installed at a customer site. In the
	next release of our sw we have to make the following types
	of changes to our schema:
	1. Add new columns to a table (both NULL and NOT NULL).
	2. Delete existing columns.
	3. Change the names of existing columns (some that appear in a key).
	4. Increasing/Decreasing the size of columns.
	5. Adding a new foreign key to a table.
	All of the tables contain data (of course).

	Does anyone have experience with these types of changes and can
	provide some words of wisdom?

	Thanks,
		parris geiser