i want to study pre-purchase influences on intention to purchase in customer behavior. do you know how can i find questionnaire to measure pre-purchase influences?
You should check google academics for any article related to the topic you are interested. For example this article 'Antecedents of consumer relative preference for interpersonal information sources in pre-purchase search" You can check in this link http://onlinelibrary.wiley.com/doi/10.1002/cb.16/abstract
Check if you could adapt the questionnaire to your study and submit it to the adequate sample during pre-test phase.
the best method is to look at litrature of studies related to your topic , you wlll find alot of choices to finaly choose the most reliable and valid questionnare.