How we change what others think, feel, believe and do
I'll think about it
Tell the other person that you will think about it. Say that you make decisions by reflection or research. Ask them for their literature and leave.
When they try to hurry you up, slow down. Tell them to slow down. Say you are a slow thinker and need time -- and do not appreciate it when people try to hurry up important decisions.
Tell them you'll be back.
That's very interesting. I take what you are saying very seriously and want to take time to digest what you are proposing.
No, I will not sign now. I never agree to such things until I have had time to mull it over.
Hurrying you up is a classic persuasion ploy. If they can get you going fast then you will not have time to think.
Framing yourself as a slow or deep thinker will frustrate the persuader, who may try even harder to speed you up and hence get themselves further into the mire.
Slowing things down is good for you too: giving yourself time to think will stop you from being persuaded by facile arguments. Avoid long-term regrets that are caused by short-term decisions.
Telling them you'll be back is also very frustrating for them. One of the sales sayings is that 'there are no bebacks'.