What if the Bride makes the declaration: Kiddushin 5b
If the groom uses a non-traditional form of speech, termd "Yad," which doesn't clearly state all of the necessary elements: Nedarim 6b
If the groom promises amount X, and then pays less, but still more than the minimum amount: Kiddushin 8a, 9a
If the groom tells her to take the money to guard it for him, and then he says it should be for Kiddushin, before/after giving it to her, where she does [not] protest: Kiddushin 12b-13a
If the groom says he will marry her after 30 days (retroactive to now) and then someone else marries her before Day 30: Kiddushin 19b
If the groom says he will marry her after 30 days, via money given now, but the money is destroyed before Day 30: Nedarim 29b
If the groom says he will marry her after 30 days, and then reneges before Day 30: Nedarim 29b
Whether a prospective groom can marry his wife "after I divorce you [from this up-coming marriage]: Nedarim 30a
The groom's right to have a Proxy do it: Kiddushin 41a, 41a-42a
Marrying a woman on condition of his not having to fulfill his requirements for food, clothing, or sexual relations: Kiddushin 19b
