What is the optimal set of database maintenance tasks for high volume of transactions
As far as the transaction log goes, I highly recommend you read this article: SQL Server Central: Managing Transaction Logs.  The biggest takeaway you should get from this is that you need to plan your transaction log backups according to:


The maximum amount of data that can be lost in the case of a disaster 
The size to which the log can grow.


The above was quoted directly from the above article on SSC.

What #1 is indicating is that if the drive that your log file exists on is corrupted and you can't salvage your log file (which means you can't back up the tail of the log for the minimization of data loss), then you will have data loss since your last transaction log backup.

And #2 being obvious, the transaction log in full recovery mode will grow until backed up.