Take care of below common conventions during development:

•Always keep your files in safe place according to file access convention.

•Avoid to include classes manually. Load it according to class and objects conventions.

•File name must be in lowercase

•Class and Variable name should  followed by camel case.

•Do not use "_" in class name except directory separator.

•Database table field name must be in lowercase.

•Use same case in model name for both Class and Query functions.

•Keep definition file name related to it's functionality. That helps to find it easily.

•Avoid to edit core code, because it can overwrite during version update.

•Keep all 3d party classes in plugin folder and adjust the class name according to the path

•If it's necessary to create a direct object then do it by __Obj method.

•Avoid to include JavaScript or CSS file in main layout. Load it as an addons.

•Create multi database connection if a particular table has to manage huge data.