Hi this is my first post in this forum and as you can see, english is not my mother language. If you want to migrate with wordpress you must follow this steps:
1. Backup the database of wordpress, if you don't know how to do, try the useful plugin for backup: http://www.skippy.net/blog/category/wordpress/plugins/wp-db-backup/
2. With a FTP client copy all the files of your current wordpress installation in your computer
3. Copy you wordpress files on DreamHost FTP space
4. Edit the wp-config.php with the correct values to use your new db on dreamhost
5. I don't know if dreamhost use phpmyadmin (I will by a plan soon), but you need to execute the backup that you made with the plugin (is a .sql file).
6. Try to go in your wordpress dashboard, I think that you need to edit the options about URL.. (if you have problems to edit from dashboard try from phpmyadmin to edit directly the table wp-options)
I think that now works.. :D