Firstly: The Best Time for Seclusion
The best of seclusion in terms of time is that performed in Ramadan, and the best of that is the one performed in its last ten nights. This is by agreement of the four schools of jurisprudence.
Secondly: The Best Place for Seclusion
The best places to perform seclusion are, first, al-Masjid al-Haram, then the Prophet's Mosque ﷺ in Medina, then al-Aqsa Mosque in Jerusalem, then the large congregational mosque. This is by agreement of the four schools of jurisprudence.
Thirdly: Worship in Seclusion
It is mustahabb for the secluded to busy themselves with acts of worship specific to seclusion,  Some Malikis and Hanbalis disliked for the secluded to busy himself with teaching, polemics, writing, sitting with the scholars, and similar acts which are not most beneficial for seclusion. like reciting Qur'an, remembrance of Allah, praying in other than the times of prohibition, and the like. This is by agreement of the four schools of jurisprudence.
Fourthly: Complete Silence
It is haram for the secluded to observe complete silence if he does this with devotional intention. This has been explicitly mentioned by the jurists of the Hanafis, Hanbalis, and Ibn Taymiyyah quoted consensus over this being an innovation in worship.
Fifthly: Marriage Contract for the Secluded
It is permissible for the secluded to conduct a marital contract, whether for himself or someone else. Consensus has been quoted over this by: al-Tahawi, Ibn `Abd al-Barr, and al-Nawawi.