The forum is chock-full of helpful posts about this. There are 2 types of remote systems, one that was port installed (when the vehicle was assembled) and one that was dealer installed (where the vehicle was sold). You'll need to identify first that you truck had the option to begin with (a dealer can tell you based on your full vin, though no Which system), and then identify Which of the systems you have. Or, you can buy one of each kind of remote and try them both.
I'm collecting my key fobs right now (2 in the mail, one here) and didn't save any of the many different threads I'd referenced, but what I remember is that there was only one system until 1999... so if you have a 96~98, you have the RS3000 (dealer installed) system, if there's one installed at all. If you do have the factory installed system (the one with the roll-down rear window), there are a lot of reports about the Chinese knock-offs not working. I bought OEM to avoid this, and you can get new cases if you want to pretty them up.
Also, the #1 issue with getting additional remotes is that the door lock actuators tend to not be up to the task of going through the motion to program the remotes. I had to replace my drivers door actuator, though you can apparently just rebuild them with new motors (4 doors for $40 vs 1 door for $110). If it's a near thing, they work better in cooler weather so do it first thing in the morning, in the shade. I think there's some sort of trick about using the key to "help" too. Something I didn't learn till after programming 1 remote is that the truck can only "remember" 4 total, so if it came with 2 originally and someone else has added a 2nd or 3rd, you may not be able to add any more without doing it via the Toyota Techstream (dealer) software. No big deal, it's $30 for the cable and stolen software from Amazon/ebay/etc, but worth knowing ahead of time (I'm waiting on that cable right now myself, opted to do the discounted price from China so I'll be waiting a couple weeks).
Anyway, search the forum, all the info needed is in here. From the different types and how to visually identify, to the FCC numbers for the remotes, programming instructions, etc... there's a sticky at the top for a "better way to search", use that for best results.
