Backup and database with RMAN and restore to the new server with RMAN. This is the best case scenario as far as migrating the database is concerned. You might want to look at using RMAN to migrate from 32 bit to 64 bit software. Also migrating with a warm backup will mean that you don't need to apply any redo, so you can just do a startup upgrade and run the upgrade scripts to upgrade the database to the new version.