How to migrate a SQL Server database?

I am upgrading / modifying my existing SQL Server 2005 database.

I would like to rename tables, change relationships in the schema and eventually migrate the data from the old tables to the new ones.

I was thinking of writing a script to :

1. change the constraints, table names
2. create the new tables 3 migrate the data from the old tables to the n开发者_JAVA百科ew ones 4 delete the old tables.

Are there any third-party tools I can use to migrate or can I do this with SQL Server DTS ? What is the best approach?