First of all, you will need to prepare some tools. I'm using:
* Clamps and holders: this helps me to hold the circuit board while soldering.
* Soldering iron set.
* pliers (long & cutter).
Scalpel blade: I use it to unseal the protective layer over the copper in the A/C remote control, to make it easy to solder a wire to it.
* Jumper wires: a suitable one to connected to Arduino board.
* resistors: I'm using 22K to protect the NPN transistor from overheating and/or damage.
* NPN transistors: any kind of NPN. Use the multimeter to figure out the E B C pins.
* Pins strip & its headers: those are goes to the base and remote control for the interaction.
* Multimeter: I use it for double check the wiring and for finding the NPN transistor pins.
* PCB board: I'm using stripboard type. It is easy to deal with, also, less soldering.
* Marker pen: It used to identify parts on circuit board.
* Drill set with its attachment: I use it for drilling hols into PCB boards. Also for cutting the back cover of the remote control for header pins.
* Drill holder (optional).
* Some screwdriver: for removing the remote control back cover. I'm using a plastic tool kit (that uses with mobile phones), it leaves no scratch on the remote body.
* Tape: I use it for holding the remote control LCD screen and protect it.
* A soft sponge tape: I use it to protect the back of the board base from any direct contact. Also for leveling remote on base.