All restores require one full backup at a minimum. That is what creates the database. Then differentials and/or log backups can be restored to the full backup that was restored.
Depending upon database sizes...
You want to do a full backup on a schedule, whether it is once a month, once a week, or once a day. The full backups make it easier to do a restore. For example, if you are doing a full backup on the first of the month and your database fails on the 25th, you need to restore the full backup from the 1st, the most recent differential (if you are doing them) and any tlogs since the differential. Now, if you are doing differentials daily, a monthly full backup isn't a big problem.
You want to consider doing differentials as they will decrease the amount of tlogs you need to restore. I wouldn't do more than one differential a day. If you are doing a full backup daily, you probably won't need differentials (however, on a critical database I was doing a full backup at midnight, a differential at noon and tlogs every hour).
Log backups. These are IMPORTANT and a must if your data is critical. Log backups are the only ones that can be restored to a 'point-in-time'. Lets say you are doing hourly log backups. Someone deletes a table at 1:15 PM. You would immediately do a log backup, then restore the full backup (with norecovery), any differential before the 1:15 Pm time (again with norecovery), then any log backup since the differential or full backup if there isn't a differential. Lastly, you restore the final log backup using WITH STOPAT and stopping the restore at a time prior to the delete.
Considerations: each differential backup contains ALL of the changes made since the last full backup. So, if you only do a full backup on the 1st of the month and differentials daily, a differential on the 25th has all the changes from the 1st to the 25th and that file could be quite large. Also, ANY full backup 'breaks the chain' of backups and restarts them. Let's say you have a schedule of: FULL once a week on Sunday, Differential once a day, Log backups hourly. Then on Wednesday, you or someone else does a full backup to move to a test server. Now the differentials and log backups made after Wednesday's full backup can not be applied to the Sunday backup. So all the differentials and log backups made after Wednesday's full backup belong to that full backup and can only be restored to that full backup. If you do not save, or are not aware of the Wednesday's full backup, then restores may fail if you restore Sunday's Full and Thursday's differential for example.
Hopefully that is clear. If not, let us know.
-SQLBill
Posting advice: FAQ481-4875