There are two useful key shortcuts for creating new line. Usually you must first move caret to the end of line and press ENTER to create new line. This is fine when you writing a line for the first time. However, when editing current line, say third word out of 10-word sentence, there's better way of creating new line. Press Command+ENTER (Mac), Ctrl+ENTER (Windows) and new line will be created moving caret to it. No need to go to the line end.

Second useful shortcut is Shift+Command+ENTER (Shift+Ctrl+ENTER respectively). When using language which lines (commands) are required to end by special character, it will be inserted for you and new line created. This applies for all C-based languages (C#, C++, JavaScript, PHP, …). In this case pressing the key combination when on the line will insert (;) at the end of that line and insert new line moving caret to it.