- Observe anti-static precautions
- Don't set fire to yourself
- Don't blame me if you break stuff
- Wear suitable gloves, avoid inhaling solvents, use appropriate ventilation etc.
- Clean edge-connectors with a cotton-bud (cue-tip) dipped in isopropyl alcohol ("IPA"/Isopropanol)
- Clean DIMM/PCI slots using a stiff piece of card (the same thickness at the DIMM/PCI PCB), wetted with isopropyl
Isopropanol is available from many chemists/pharmacists.
You can also buy commercial connector, and PCB cleaning solutions and devices.