Stuff you'll need for a head unit install:
Head Unit
Head unit wiring harness
Brackets
Install Supplies
Vehicle wiring harness
Stereo install kit (Most of the time)
Antenna adapter (Sometimes)
Optional Supplies
RCA Cables (If you're installing an amp)
What it is:
Head unit: The CD / DVD / Cassette in-dash receiver
Head unit wiring harness: Included with the head unit; Connects to the back of the head unit
Vehicle wiring harness: Purchase separately from head unit. Connects to your vehicle's wiring harness
Stereo install kit: Purchase separately from head unit. Adapts your new head unit to the original radio's location.
Antenna adapter: Purchase separately from head unit. Used to adapt new head unit's antenna plug to vehicle's antenna lead.
RCA Cables: Used to connect your head unit to an external amplifier.
Tools / Supplies:
Assortment of screwdrivers, wrenches, etc.
Wire cutters
Wire strippers
Wire crimping tool
Panel removal tools
Soldering iron (opt.)
Crimp caps or solder
Electrical tape
Basically, this is what you need everything for:
Head Unit Wiring harness: To connect head unit to power, ground, speakers, turn-on, etc.
Brackets: To be sure head unit is securely mounted to vehice
Vehicle car harness: To connect head unit to power, ground, speakers, etc
Stereo Install Kit: To mount head unit to vehicle's stereo location
Antenna adapter: To connect head unit's antenna plug to vehicle's antenna
RCA Cable: To connect head unit to external amplifiers
Tools:
Screwdrivers / Wrenches: To screw and unscrew panels, brackets, etc.
Wire cutters: To prepare wiring
Wire strippers: To get wires ready for soldering / crimping
Wire crimper: To splice wires together by crimping
Panel removal tools: To remove panels without damaging them
Soldering Iron: To splice wires together with solder
Crimp caps: To splice wires together with crimp caps
Solder: To splice wires together with solder
Electrical tape: You might need some at some point!