What is the best scenario for database backup?

Dual, daily incremental backup with one copy on site and the other offsite with attention to the lifetime of the used media, and a monthly resorability test.

for orgnisation which size small, i prefer to make full daily backup with overwrite, for medium full daily backup without overwrite and for big size and stretegic database i suggest ot take full backup with log and datafiles hourly and also suggest to backup drive is not same for full backup log files and datafiles.

Daily incremental Backup(T log),Weekly differentail backup, Monthly full backup with integrity check.

Keep backup to a tape or offsite also.  

Then remove older backup files by keeping a offsite backup. 

It is good practice to back up to disk, transfer to tape and store tapes offsite for disaster recovery (DR). The backups to disk are faster; DBAs have more control and can better monitor these and, with this method, DBAs hold two sets of backups—one on disk, the other on tape.

During restore, if backups are still on disk, it will be a faster restore, reducing mean time to recover (MTTR).

Real Time remote site backup 

If possible daily full backup and incremental backup hourly

best = depends on budget; for me = (local replication + remote replication) on separate servers

The best senerios for database backup is to get the most consistent backup of the database with little no performance issue.

In order to achieve this scenerio you need to have production and disaster site configured for the database.

The backup of the database is best taken from the DR site to ensure zero performance issue with the production. Since the backup is running from the DR site you can schedule several incremental and full backups  in accordance with transaction rate of the database.