Internal

Methodology

Set up the performance testing environment.

Start a diagram document, and Environment text document and a "Finding and Recommendations" document.

Map it (Performance Testing Environment.odg)- get a diagram that shows:

Hosts (names, IP addresses/subnet masks, external ports).
Represent all network interfaces and their connectivity to various networks. It helps to understand how the hosts are interconnected - on the diagram.
Represent processes
- Load Agent
- Proxy
- Application Server
- Database
Document the procedures to stop/start the processes - some load tests may need the processes to be completed shut down and restarted. Usually there's an "Environment" document associate with the environment where all these procedures are documented.
Encode log locations as aliases (al, jbl, etc.)
If the target are Windows machines, it's a good idea to install Cygwin - it'll improve productivity and provide a lot of good tools.
Annotate the environment diagram with the RAM and CPU amount on each host.

Identify the application server configuration file and its location on disk.
Represent the database connection pools and the connections to their respective databases on the diagram. Their min pool size and max pool size are also useful so represent them as [10-100] on the diagram. For JBoss, look for jboss:domain:datasources.

Put in place monitoring for CPU, physical RAM, open file descriptors and other system resources.

Use a load generator (JMeter, Load Runner, NeoLoad).

Start with simple scenarios:

Middle of the road for baseline.

Specific usage scenarios, maybe?