There is no. of things which are small but very important in SEO:-
1. Domain life: Domain life is very important. A domain life should be more than 2 years. It puts a positive impact on google, if you buy your domain for more than 2 years.
2. Server Response time: Your web server where your website is hosted should be uptime and well maintained so your website could not be down for a while. IP address of a server also affects your website e.g. if your website is hosted on a shared hosting where many other website hosted, IP address of the all shared website would be same. In shared hosting if any website will do any illegal thing google will black list that IP address who is hosting that website and in this case your website will also get affected (due to same IP address). So, if your website is hosted on VPS or dedicated server then this kind of problem will not bother you.
3. SEO Friendly URL: A web site should have SEO friendly. URL should like www.example.com/mobile-app-development/ not like www.example.com/page=home?id=10 etc.