RefactoringUI series already mentioned is great for specific tactical tricks that are immediately applicable.
To develop a deeper understanding and taste, I would recommend "Design Basics" by Lauer & Pentak. I’ve studied and taught design from it and think it is a great introduction to the fundamentals. The latest edition tends to be overpriced as a general rule. I would go for one of the older editions. Personally, I don’t think the content improved any after the 5th ed (which is excellent). Immersing yourself in that kind of content can give you deeper understanding of why specific suggestions from folks like RefactoringUI work as well as they do and develop sensitivity in perception.
To develop a deeper understanding and taste, I would recommend "Design Basics" by Lauer & Pentak. I’ve studied and taught design from it and think it is a great introduction to the fundamentals. The latest edition tends to be overpriced as a general rule. I would go for one of the older editions. Personally, I don’t think the content improved any after the 5th ed (which is excellent). Immersing yourself in that kind of content can give you deeper understanding of why specific suggestions from folks like RefactoringUI work as well as they do and develop sensitivity in perception.