Determine your backup strategy by the requirement for the restore (RPO and RTO). How much data is allowed to be lost (= RPO) and how long is data to be allowed unavailable (= RTO). Brent Ozar has some nice articles about it, like The 9 Letters That Get DBAs Fired[/url].
If your RPO is like 15 minutes, you'll need to schedule your LOG backups at least every 15 minutes. If your RTO is 30 minutes, you'll need to be able to restore the FULL, DIFF and all LOGs within that 30 minutes.
Edit: fixed the link
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