Whether the upper part is left or right depends on how the horizontal batch is written. If the horizontal batch is written from right to left, the upper part should be posted on the right.

If the horizontal batch is written from right to left, the upper part will be posted on the left.

In addition, in addition to the requirements of antithesis, couplets should generally be flat on the top and flat on the bottom, that is, the tone of the upper couplet should rise and fall, and the tone of the lower couplet should be flat.

Extended data:

According to different local customs, the time for posting Spring Festival couplets is slightly different. As the saying goes: "Twenty-eight, applique", and in some local folk songs, there is also a saying that "Twenty-nine, paste the unitary (meaning paste the Spring Festival couplets)".

Spring Festival couplets and the like are posted on the 28th and 29th of the twelfth lunar month, but most of them choose the posting time according to their own schedule. "Rich everywhere, blessed with auspicious family photos."

According to Putonghua, the upper and lower couplets all end with the second intonation, and even the tones can be distinguished according to the horizontal rhyme. Only when there is no horizontal approval and the upper part is weaker than the lower part can the upper part be used.

Sticking Spring Festival couplets is the first thing for China people to celebrate the Spring Festival. Whenever the Spring Festival approaches, every household will put brand-new Spring Festival couplets on both sides of the gate, with black characters on a red background, which is steady and bright.

References:

Baidu Encyclopedia-Spring Festival couplets (usage)