Edit: The following will only apply if you are always on the same network. It won't work in Starbucks; but neither will any other solution.
Simplest would be to set it to use DHCP with a manual address, from the Network System Pref pane.
To prevent any conflict, set it to the address is currently has assigned to it, which shows in the top part of the panel. [Hit Apply to save.]
That way it will behave just the same way as full DHCP, but will just make sure it hangs onto its address. Even though there is potential for another machine on the same network to possibly be given that address by the DHCP server, it actually rarely happens, as the existing reservation usually lasts long enough to prevent it, & routers 'prefer' to assign the same address to the same device anyway.
You could poke in the router to find how to set up a static mapping for the Mac, but the chances are you won't ever actually have to.