You will need to be able to solder, understand circuit diagrams, possess a basic knowledge of electricity and electronics, and be able to use a multimeter.
Soldering is a skill you may not have and which can only be obtained with practice. Maplin Electronics (
www.maplin.co.uk) sell some basic projects that can help.
You should also possess dexterity and be able to manipulate component leads and small wires, again the Maplin projects can help you.
Some kits are easier to build than others. PCB ( printed circuit board ) based kits with clearly marked component locations and coloured wiring locations are easiest. With a PCB all interconnections are made between components by fixed tracks thus reducing build errors.
"Hardwired" kits using tag boards are really not recommended for beginners unless you are patient, careful, and willing to learn as you go. Component locations and mechanical fixings have to be thought out as does the wiring between components.