When dealing with a complex codebase, it is beneficial to focus on solving one specific issue at a time before delving into the entire code. By concentrating on a narrow problem area, one can enhance understanding and make efficient fixes. It is also recommended to take a vertical slice approach to understand the necessary parts of the code for the current task rather than trying to grasp the entire system at once. Another useful strategy is to create a reproduction of the problem and step through a debugger to gain a higher-level understanding of the data flow without needing to comprehend every single function or class.