Correct way to attach speaker wires... Wait, what!!!

Hi Autre, WBT is a famous German connector manufacturer.

http://partsconnexion.com/connectors_brand_wbt.html

All connectors degrade sound. All, regardless of cost. Bare wire is best. Do the comparisons and it is obvious. So, go with bare wire.

1) just clean every so often and no oxidatiobpn issues.
2) or just thin the stripped area - good option

You can buy some very good sounding tinned speaker wire from Duelund. Their 16 gauge stranded in cotton wire.  Makes great speaker cable and costs $10 meter.  It is tinned already.  You can buy it from Parts Connextion if interested. 

The wire of your choice cold welded (method used by Audioquest) to thin pure silver spades.  Tighten down but not to the point that you deform the thin silver spades.  Listen and enjoy!

After doing a lot of testing with different types of power cord and interconnect connectors, I do not actually believe that bare copper against bare copper would be the best solution.  It really depends on what your speaker binding posts are.  Bare copper against bare copper (two different pieces of metal under physical contact) does not really transfer higher frequencies as well.  This is where plating increases the ability for high frequencies to jump from one piece to another (i.e. bare copper against rhodium/gold/silver plating).  The plating just dictates the type of sonic signature you're after.  Gold plated binding posts could be good, but if it's pure brass, then you can probably improve by using a plated banana/spade.