Tips: Whenever you change guitar strings, always do it 3 at a time. Do not take out all 6 at one time.
Reason: Your guitar neck will WARP (simple terms: bend) due to sudden release of tension of the 6 strings.
When that happens,
- your strings may get a high possibility of buzzing when you play due to unnecessary contact with the fret board at the wrong places.
- you may find it hard to tune to the correct standard tuning and whatever chords and notes you play will sound wierd and incorrect.