Waiver and waver are homophones, but they mean very different things. I often find that waiver is used when the writer actually means waver – I presume the mistake is made because the writer has the ay sound in mind.

Waiver

• the act or an instance of giving up a claim or right
• a document recording the giving up of a claim or right

Waver

• to hesitate between possibilities; to be indecisive
• to swing from one thing to another
• to become unsteady; to falter; to become weaker
• to move back and forth or one way and another; to quiver or flicker

My tip: try to associate waiver with the giving up of a claim. It should be fairly easy to remember that waver is the spelling for everything else.