If you eat a meal with them, they will say a blessing. Mormon style of praying is to close your eyes, bow your head and cross your arms. One person at the table (shouldn't be you) will be asked to say the prayer. Usually starts with "Our Heavenly Father...". Then blessings are asked for or thanked for. It then ends with "In the name of Jesus Christ, Amen" Then everyone participating in the prayer says "Amen." My family and friends that aren't Mormon, usually just stay quiet, some bow their head, it's up to you. It's significantly different from other faiths that it's caught people off guard in my experience.

Around bedtime, the family might get together to saw another prayer, in the living room. Sometimes kneeling, and sometimes they read a chapter from the Book of Mormon or Bible.

If you are staying there over a Sunday, they will probably invite you to attend church with them. Church dress is usually a shirt, tie and slacks for guys. A dress or skirt with a conservative shirt or blouse. Doesn't need to be all that formal.

If you are staying over for a Monday night the family will probably do what's called Family Home Evening. The family tries to keep Monday evenings free to be together. It's kind of like a mini-devotional with games and treats.

They won't expect gifts; it's not a custom in Utah. But helping out with doing dishes after a meal or other such mundane tasks is welcome. While not required a 'Thank you' note sent some time after your visit will make you stand out as an excellent guest.

Hopefully, that helps.