What is the ruling on adopting the opinions of shaykhs in matters of marriage such that their word, whether in rejection or acceptance, is binding, and is it permissible or forbidden to ask a shaykh about one's destiny?

If the consultation is with sheikhs and people of religion and sound opinion concerning matters of marriage and the like, then this is commendable and part of the Sunnah (definition). However, if the consultation is with soothsayers and diviners who claim to know the unseen, then this is forbidden and one of the gravest major sins. Severe warnings have been issued against those who approach them or believe them, because they claim knowledge of the unseen, which Allah alone possesses.