Start with your hardware: Turn the PC off, unplug everything, and then find an open area to do your dusting and cleaning. Either with a laptop or a desktop, the focus will most probably be the keyboard and the mouse or the trackpad. Cleaning them should be trouble-free since a lot of household products available in supermarkets, can be used.
Cleaning should also include the inside, and sometimes not-so-easy-to-reach parts of the computer, to keep everything clean and working quietly. However, in the case of a laptop, expert skills are essential to go and clean the inside parts. Referring to the manual for information on taking out the parts or referring the laptop to technicians is most preferable.
Untangle those wires: When all the cleaning is done, before re-arranging the parts, take some time to untangle and organize the wirings. Shorten wires by tying them just enough to reach the plugs. The rain gutter method and the IKEA Signum cable manager can be used, depending on the workspace. In the case of a laptop, using some binder clips on the desk can help a lot in saving wires from falling on the floor and making a mess.