In OLTP environment, where read is more frequent than write, the Cluster index is your biggest gun and your major weapon. Over the decades its best usage is well known...

Some considerations:

1.Size of table and growth rate.

2.Primary needed for speed of replication?

3.OLTP vs. Data Warehouse like

4.3rd normal form vs. Demoralization?

5.Contention with other servers and process?

Sometimes you may want to ask:

...

The difference between hierarchy database and relational database should tell you why no one should be in that school #2.

The real 2 or 3 schools in question should have been...

With comments like this I run for the exit:

… good clustering. One school says to put the clustered index on the column or set of columns that would be most...