Protect yourself from low appraisal

[Leo Don]

hello BP, 

I am just curious to know how to structure a contact in order to protect yourself from low appraisal and also how to make seller responsible for fees associated with the appraisal cost in case they don't want to agree to adjust the price. 

I am aware as a buyer you can alway walk but however the appraisal cost that a buyer paid for an appraisal is there anyway to get recompensated for it?

Thanks for any inputs.