Back up with pg_dump -F c -f backup.dump dbname and restore with pg_restore. Test your restore regularly — an untested backup is not a real backup. Store backups off-site on cloud storage like S3 or Backblaze.
Backup and Restore
# Backup single DB
pg_dump mydb > mydb.sql
# Backup with compression
pg_dump -Fc mydb > mydb.dump
# Backup all databases
pg_dumpall > all.sql
# Restore
psql mydb < mydb.sql
pg_restore -d mydb mydb.dump