There are a few points in your Tacoma build to start considering upgrading your differential. A properly upgraded differential is important for maintaining throttle response and increasing it as well as improving off-road performance. A good way to gauge what you need for your Tacoma is to take into consideration what mods you intend to throw at your truck and how you intend to use it.
Ring Gear: With a Tacoma you will almost always be throwing a lower ring gear in your differential. Heavy add-ons, suspension mods, and off-road tires will bog the engine down and a lower ring gear will restore throttle response. Going lower will also be necessary for off-road use as it will increase throttle response at low RPMs.
Carrier: The differential carrier can be replaced if one is looking to maximize traction. With a truck that is used both on and off-road a limited slip will almost always fit the bill. The limited slip will send power to the wheel with the most amount of resistance, but will still send power to both sides. An open differential sends power to the wheel with the least amount of resistance and will almost always be replaced.
Lockers may also be considered as they allow one to switch back and forth between an open and locked differential on command. You will want to consider modifying the differential when you begin diving deeper and deeper into hardcore off-roading.
Axles: The stock axles can take a beating but may fail under hard use. If you know you will be heavy on the throttle in low traction scenarios. By upgrading to sturdier axles, you will prevent the Tacoma from chewing through axles when traction is suddenly gained.