Wedding ceremonies have two legal requirements; the signing of the register and the vows. Whilst both civil and church ceremonies allow for some variation on the traditional vows, the declaration and contraction must be said by both the bride and the groom in order for the marriage to be legal. The minister or registrar will ask you to repeat them in parts, but it makes sense to read through them before anyway. They are as follows:
Declaration: I do solemnly declare that I know not of any lawful impediment why I, ..., may not be joined in matrimony to ...
Contraction: I call upon these persons here present to witness that I, ..., do take thee, ..., to be my lawful wedded husband/wife.