Skills in problem solving, including finding and applying the appropriate knowledge to a problem, are important learning outcomes from the completion of a Physics degree at University. This thesis investigates the characteristics of successful and unsuccessful novice University students solving problems in Physics in various contexts. Gaining an insight into student behaviour can clarify areas of weakness and potentially provide research based instructional strategies in these contexts. Access to external information during problem solving, such as the Internet, is becoming an increasingly relevant research area, as students use resources for homework questions and then in employment after University. Three chapters (Chapters 3-5) investigate individual novice problem solving with and without resources, such as a textbook. Participants were from introductory years one and two of Undergraduate study at University. The results from this chapter show successful and unsuccessful approaches by students to multi-step problems. One notable result is that unsuccessful students demonstrated an inability to apply the appropriate physics concepts, with or without the availability of resources. These results have implications for the skills required in closed and open-book exams. Three chapters of the thesis focus on the analysis of Peer Instruction (Chapters 6-8), an instructional method designed to improve conceptual understanding. Peer Instruction was used with a first year Introductory University class. Technical word use was not associated with success on Peer Instruction questions. Conversations were also analysed qualitatively. The results reflect diversity in reasoning regardless of correctness on the question. Some recommendations for the implementation of Peer Instruction are presented. The thesis is organised as follows. A literature review was conducted in relevant areas of study and is presented to set the context of the work. Three chapters report the study with novice individuals solving multi-step problems with and without resources. Three further chapters investigate successful and unsuccessful Peer Instruction discussions in Physics. The final results chapter (Chapter 9) presents a study of a group of experts solving physics problems. Overall successful and unsuccessful problem solving strategies were compared, as well as preliminary comparisons between expert and novice behaviour when solving physics problems.