Machine learning is the science of algorithms that detect patterns in data in order to make accurate predictions for future data. I think the following technical skills are a must:
- Querying handling data-sets of up to 1M rows and visualizing data of the same size.
- Skills in linear algebra and logic as most of the algorithms rely on these two areas in math.
- An understanding of optimization algorithms.
If you are looking to start an academic career in machine learning, I recommend applying and attending one of the many machine learning summer schools – they are the fastest way to get a full overview of all the state-of-the-art algorithms and approaches and they typically also have a session on applying machine learning in practice.
If you are looking to start a machine learning career in industry, a good thing is to either participate in a Kaggle competition, try contributing to OpenSource ML projects such as SparkML or Theano (or start one yourself) or try to get an internship; all of these allow you to get first-hand experience in building models, modifying algorithms and iterating to improve accuracy. There is a huge demand for people that would like to work in the field of machine learning and employers typically look for people that have demonstrable interest.