What shell do you use? Depending on the shell, there will be an initialization file that is run whenever you log in. For the bash shell, it's .bashc. For the C shell, it's .cshrc. Etc.
In your shell's initialization file, put the necessary lines to set the Perforce settings.
For example, in a bash shell, you'd add things like 'export P4USER=bryan', 'export P4PORT=perforce.mycompany.com:1666', etc.
As an alternative, you can use P4CONFIG files. Then you only need one line in your shell initialization file, to set 'export P4CONFIG=P4Config.txt', and then in the working directory where you have your workspace files, create a file named P4Config.txt and place the remainder of the P4 environment variable settings there: P4USER=bryan, P4PORT=perforce.mycompany.com:1666, etc.
Use 'p4 set' and 'p4 info' to confirm that all of this is working as you expect.
Here's more documentation: http://ftp.perforce.com/perforce/r13.3/doc/manuals/p4guide/chapter.configuration.html