How will you know about the Clinical Trial safety before participating?

Every clinical trial is conducted to test the efficiency and safety of the unknown drug. The common concern of participants would be the safety of the trial that is conducted. It is understood that the clinical trials are conducted under the supervision of the expert health professional and safety of the participant is assured here. The volunteer of the clinical trial should be assured about the safety of the clinical trial before participating in the medical trial. How will this happen? how can one be assured about the safety of the clinical trial that is happening? 

The volunteer of the medical trials should know if the trial has got the approval from the FDA, safety of the protocol, history of the clinical trial testing. The participant should also be educated about results, benefits and side effects of the clinical trial, in charge of the clinical trial, number of visits and the liability to stay with the trial till the process is completed.