In preparation I place a towel on my desk to protect the guitar and use a guitar neck support (Ebay) to keep the guitar from moving too much.

The tremolo arm can get in the way when the guitar is turned over, so I remove it and stick cello tape over the hole to retain the spring I use.

I tend to replace 1 string at a time. This I feel is particularly important on my old '65 Hofner, as it keeps tension on the neck through the whole process. Going from full tension no none by removing all the strings at once may flex old joints and glue and damage the guitar. Changing 1 string at a time also leaves other strings for rough comparison of pitch while tightening each string. Strings usually only break if over tightened.

When fitting each new string I fit it through the hole and up to the appropriate tuning post and cut it to length 2-2.5 inches passed the post. This is enough left to wrap around the post.

The string passes around the post on the left, so the string is tightened counter-clockwise. If the hole in the post is horizontal, I pass the string through the hole and I try to bend the string down towards the headstock and cover it with later turns. Not always possible. If the hole is vertical then push the string into the hole and fold it into the slot.

I add turns until all the slack is removed and then test the string against adjacent strings to get approximate tuning. Bear in mind that the remaining 5 strings will have tightened and raised pitch slightly as the spring tension on the bridge will be the same, but the compensating strings tension reduced whilst the string is being fitted.

When all strings are fitted and roughly in tune, I stretch each string sideways ( around 2 semitones) a few times and then retune. I do this process 3 or 4 times.

I often need to retune in the first day or so.

I hope you find this helpful.