SQL Server max memory, page file, max degree parallelism
Your 3 questions touch max memory, page file and max dop setting.

MAX MEMORY



If the server is dedicated SQL Server only without Analysis services (since  SSAS is another beast), then Glenn's recommended best practices is a good starting point. For additional components, you should refer to Jonathan's blog on how to configure max memory.

I have answered on SQL Server Maximum and Minimum memory configuration. This will be helpful if you have lots of SSIS packages running on your server instance.

Page File



I normally set it away from C:\ drive on the drive which has sufficient disk space. I agree with Remus and Brent's recommendation. It should be PAGE FILE FOR SQL SERVER = 1.5 * RAM. A page file will be useful when you encounter yourself in a situation wherein you have to take a FULL MEMORY DUMP (normally asked by Microsoft CSS) for troubleshooting.

Read How to determine the appropriate page file size for 64-bit versions of Windows KB 889654 thoroughly and Buck Woody talks about page file here.

MAX DOP Setting



For sharepoint its recommended that maxdop = 1 be set instance wide. For a normal sql server, I would suggest you to follow  - What is a good, repeatable way to calculate MAXDOP on SQL Server? I have a script written which will calculate it for you.

The gist is below (KB 2806535 also mentions the same thing):

8 or less processors    ===&gt; 0 to N (where N= no. of processors)
More than 8 processors  ===&gt; 8
NUMA configured         ===&gt; MAXDOP should not exceed no of CPU’s assigned to each 
                                 NUMA node with max value capped to 8
Hyper threading Enabled ===&gt; Should not exceed the number of physical processors.


As a side note, I would suggest you to read  - Recommended updates and configuration options for SQL Server 2012 and SQL Server 2014 with high-performance workloads