Best practices of user interface (UI) and database integration

I've completed the design of my web application's UI and database schema, and I'm about to start with their integration.

I'm building a web application for the first time and in the process I've realized that I've made many mistakes which could have been otherwise avoided by simply doing some research. However, in the above mentioned integration aspect I didn't find any informative post.

I believe in the philosophy of smart learning from mistakes made by others and those who are experienced.

What suggestions, tips and good practices I must follow in order to integrate my UI with my database successfully with least errors. Any suggestion will be appreciated. :)

Please, don't close this question. I'm sure it will benefit many other beginners like me.