I typically replace the female connectors if possible, saving old ones for reuse.
Remove a pin, cut old crimp contact off, strip to length, crimp on new pin, insert pin into new housing.
Following this one for one process, you'll ensure the correct order is maintained.
Once the old housing is completely empy, I'll wash them in vinegar.

For the male sides, remove the board.
Sand the edge connector lightly to remove any corrosion, dirt, whatever.
"Tin" the copper strip by melting solder onto it, and while still molten wipe it off with a paper towel. Make sure you don't build solder mounds. Be careful to not apply too much heat as you can fry the copper from the board.

Good luck.
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Chris Hibler - CARGPB #31
http://www.Team-EM.com
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The new place for pinball repair info

A reasonable question...I don't want to completely empty the connector while repinning. I want to do one pin at a time. Once I've transitioned each pin to the "new" connector, I bath the old one in vinegar to remove any hint of alkaline residue.

System 1/80 connectors are very reusable. You just need one extra to get started the way I prefer.

There you have it...
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Chris Hibler - CARGPB #31
http://www.Team-EM.com
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The new place for pinball repair info

"Cleaning" header pins if significantly tarnished, is not feasible. Simply replace them. If you sand them, you'll remove the finish and the "fix" will be short term. You can use a pencil eraser on them for light tarnish.
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Chris Hibler - CARGPB #31
http://www.Team-EM.com
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The new place for pinball repair info

@alonzomoselyfbi, the post directly above this is what I use.
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Chris Hibler - CARGPB #31
Http://chrishiblerpinball.com/contact
http://www.PinWiki.com/ - The new place for pinball repair info

You can reuse the connector that you have now.
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Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact
http://www.PinWiki.com - The Place to go for Pinball Repair Info

I need to document this for the PinWiki.
Use a small screwdriver to release the "tang" that locks the pin in place.
Pull the wire free from the connector. If you are lucky, the pin will come with it.
Use serrated tip needle nose pliers to grab the pin and pull it out.
That's it.

You can clip some of the connector off to clean it up a bit.
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Chris Hibler - CARGPB #31
http://ChrisHiblerPinball.com/contact
http://www.PinWiki.com - The Place to go for Pinball Repair Info