Speed and reliability issues come in many forms.  We analyze each of these to come up with the appropriate solution.

Backups

Backups are often set up as some automatic event that is rarely looked at.  "My IT guy copies everything in this folder to an off site backup."  What if the data in that folder is outdated or simply doesn't work?  I have seen people lose years of data because they had no idea that their backup wasn't working as expected.  SQL Server can be set up to automatically restore backups to another database to ensure integrity.  It can also be set to email a list of people upon failure and to do a variety of other things so the loss is typically minutes, not days or hours.

Disk Latency

If you Google this, you will find that usually at around 20 ms people start considering this to be a problem.  There are a lot of potential causes, so don't buy a new hard drive just yet!  <G>

Not Enough Memory

SQL Server will cache data for quicker retrieval.  When not enough memory is present, SQL Server will dump the data and go after the disk again for additional queries looking at the same data.  Reading from the disk as opposed to memory is hundreds of times slower.

Improperly Allocated Memory

SQL Server will take almost all the memory on the box or virtual instance it is installed on.  In fact, Microsoft claims to the contrary, it will take so much that your OS may actually have IO and network speed issues due to lack of resource and excessive paging.​  While it will eventually back off, it is generally too little, too late.

Individual Queries

Often a single report or query will take a long time to run.  These are typically the first ones people notice and look to focus on.  Improvements are readily apparent.

Repetitive Queries

​These are less apparent, but may easily result in more lost time than the rarely run report or query.  It may be the code that runs when you open a screen or navigate to a search.  Since Total Time Lost is Time Lost times the Number of Occurrences, a report taking 5 minutes run once a week, is less damaging than a 5 second loss 20 times a day.