What are the conditions of deliberate practice? TL;DR: What are the necessary and sufficient conditions for deliberate practice?

Longer version:
I've read a number of books/articles on deliberate practice and its role in acquiring expertise.  The texts make a compelling case for the argument that a minimum of 10,000 hours of deliberate practice is required to develop expertise in a particular field.  The implication of the research is undoubtedly optimistic (as it largely dispels the notion of being born talented - with certain semi-exceptions, notably, athletes).  However, I struggle when it comes to translating the research into practical takeaways for myself.

As someone who'd like to apply the concept of deliberate practice to his profession/hobbies, it would be useful to have a rigorous/comprehensive definition of deliberate practice that I could effectively use as a check-list.  But in the material I've read, it seems that "deliberate practice" is effectively defined as (and I'm paraphrasing): "the type of practice of which 10,000 hours are needed in order to develop expertise".

So, to put it differently (from the TL;DR above):
How do I know if I'm practicing effectively?  (Aside from practicing a certain way for 10,000 hours and seeing if I become an expert)

Disclaimers: 


It's probably evident from my post that I'm not a professional
researcher / academic.  My exposure to the topic is largely from pop
science books that cater to the mass-market (i.e., I'm trusting the
authors re: the quality of underlying research).   
Also, the answer to my question may well be addressed in formal research papers found
on PUBMED/etc., but I unfortunately don't have access to that.
My causal impression is that the literature on deliberate practice is a little vague about how deliberate practice differs from other forms of practice.

I think it was Ericcson who distinguished between work, play, and deliberate practice. Work is to get something done, play is for enjoyment, and deliberate practice is activity completed with the goal of improving skill.

A few general features of deliberate practice include: 


It should be effortful and is likely to involve a degree of focus
The intensity and focus of deliberate practice may limit the amount of time that can be dedicated to it per day, and it is important to get appropriate rest either side.


Deliberate practice is generally designed to be at the optimal level of challenge given your current ability. It should also include feedback.

In general it is going to help a lot to have a tutor. Tutors go by many names: coaches, supervisors, mentors, trainers, teachers, and so on. The tutor can assist in providing you with appropriate exercises and giving you the right feedback. So for example, music instructor may push you to master specific exercises or get you to master a particular musical piece because they can see that it will challenge you. Similarly, a tennis coach may get you repeating particular strokes with feedback.

That said, if you don't have a tutor, you can still attempt to apply the principles of deliberate practice to your own learning. It's harder and probably less efficient, but it is possible to teach yourself a lot of things. A few general suggestions:


Be clear on the skill you're actually trying to master. What is the goal state? What would be evidence of you achieving that state? For example, in academia, evidence of achievement might be seen in getting some top-tier publications. In golf, it might be achieving a certain handicap.
Try to create learning environments where you get feedback on your performance. For example, when doing mathematics exercises you get feedback. When you submit journal articles you get feedback through peer review.
Reflect on whether the activities you are doing are actually improving your skill. Be mindful of when you are getting stuck in a rut. Explore learning materials that might be useful.


I'd also make a final point about the importance of actual work in acquiring a skill. The deliberate practice literature does have a tendency to emphasise the importance of drills and background study (e.g., practicing your serve; studying famous chess masters, etc.). However, in many cases, actually doing the activity (i.e., that which is called work) can be an incredibly valuable learning experience. I vaguely recall a study that looked at soccer referees that showed that number of matches refereed was an independent predictor of referee performance over and above deliberate practice.