Design Pattern's,

Code Smells

Few Books

Design patterns are optimized, reusable solutions to the programming problems that we encounter every day.

You have a problem statement - and you have a solution

Do not force design pattern

Understand how design patterns are defined in first place, and help yourself to come up with a variant of a solution.

Here comes some philosophical rant?

Pattern - is a solution to a problem, based on principle(s) and a valid context.

A fundamental truth or proposition that serves as the foundation for a system of belief or behavior or chain of a reasoning

Software Design Principle or Object Oriented Principles or any other principles

If Principle is Science, Design Patterns is applied Science - easy to relate to and understand
Principles like Science is very vast in nature, Applied Science is very narrow in scope and easy to study
Study Design Pattern and try to understand underlying principle behind it
Mostly for design - OOP's Principles are good to understand design patterns
Study of Craig Larman's work will also help
Universal principles like - YAGNI, DRY, Rule of 3 also helps in understanding mindset of author of pattern

Patterns to understand where is problem in coding

Code Smell	Refactoring Pattern
Alternative Classes with Different Interfaces	Unify Interfaces with Adapter Rename Method Move Method
Combinatorial Explosion	Replace Implicit Language with Interpreter
Comments (a.k.a. Deodorant)	Rename Method Extract Method Introduce Assertion
Conditional Complexity	Introduce Null Object Move Establishment to Decorator Replace Condition Logic to Strategy Replace State Altering Condition with State
Data Class	Move Method Encapsulate Field Encapsulate Collection
Data Clumps	Extract Class Preserve Whole Object Introduce Parameter Object
Divergent Change	Extract Class
Feature Envy	Extract Method Move Method Move Field

Code Smell	Refactoring Pattern
Duplicate Code	Chain Constructors Extract Composite Extract Method Extract Class Form Template Method Introduce Null Object Introduce Polymorphic Creation with Factory Method Pull Up Method Pull Up Field Replace One/Many Distinctions with Composite Substitue Algorithm Unify Interfaces with Adapter
FreeLoader (Lazy Class)	Collapse Hierarchy Inline Class Inline Singleton
Inappropriate Intimacy	Move Method Move Field Change Bidirectional Association to Unidirectional Association Extract Class Hide Delegate Replace Inheritance with Delegation