This is very important and crucial task from SEO point of view while you are moving your entire old domain to a new domain name. This is always a very difficult task to perform for a webmaster but following these steps will prevent your website to hurt from natural search engine.
1. Once you complete with moving all content to a new domain name then write a code that will redirect your old domain to newer one. You are permanently moving your website to a new domain so make sure you are using 301 Redirect (Permanent Redirect).
2. Once this is done, check if its work properly. You need to create page by page 301 redirect so Search Engine and Users can find exact corresponding page.
3. Add your new domain to google webmaster tool and verify it and then upload sitemap, so google find your new domain and crawl every pages.
4. Check regularly crawling report in Google Webmaster tool and check if google showing any 404 page for your old domain, if you find any 404 page then create 301 redirect page.
5. Once everything done with Google and other search engines check back link of your old domain and contact webmasters to let me know that your website moved to a new domain and ask them to change the link back url.
6. keep control on your old domain up to 180 days.