There are many solutions online to redirect all the traffic from your old website to new website safely. The method below is one of the bulletproof ways that is sure to work. It will make sure all traffic is redirected from the old domain to new domain. Just plug this into notepad and save it as a Htaccess file on your old domain.
Its very important to perform these changes so you can keep your google rating on the new domain. Here is a list of some scenarios and the code needed to make it work. Use the one which fits your case the best.
Redirect from www.olddomain.com/thispage to www.newdomain.com/thatpage
Redirecting from www.olddomain.com to www.newdomain.com
Redirect from www.olddomain.com/thispage.html to www.newdomain.com/thisfolder
Redirect from www.samedomain.com/thisfolder/thispage.html to www.samedomain.com/newfolder/newpage.html
To change from .php to .html file extensions
To redirect from www.samedomain.com to samedomain.com (removing www extension)
To redirect from samedomain.com to www.samedomain.com (adding www extension)