1. Copy files and database to new location.
2. Change BASE_URL and BASE_DIR constants in ip_config.php file (you may also need to change database connection constants).
3. Go to Administrator -> System and clear cache.
4. Make folders "audio", "file", "image", "video" including subfolders and files writable.
5. Change robots.txt

It's really that simple.

If you don't know what to write in BASE_URL and BASE_DIR constants on your new server, upload get_config.php file into root directory of website and access it with your browser (e.g. www.example.com/get_config.php). You will see those two values generated on the screen.

Stéphane Moureau wrote more detailed manual on how to move ImpressPages website from your development environment to client hosting server.