There are three main practice planning tools which should be utilised when planning your practice sessions.

CPA - Career Path Analysis.

This tool aims to get your short (6 - 12 months), mid (1 - 2 years) and long (2+ years) term goals wrote down and categorised.  This will help you decide what your priorities are and write specific goals relating to your priorities.

SWOT Analysis (Strengths, Weaknesses, Opportunities, Threats)

The SWOT analysis is also very useful to discover and work on weaknesses in your personality and playing.

SMART analysis (Specific, Measurable, Achievable, Relevant, Time)

A SMART analysis is used on more general playing goals that relate to your CPA, or for very specific technical aims. It’s particularly useful when deciding if a certain technique needs a lot of attention – it is pointless wasting time on something you are already great at or working on a technique that will be of no use in the long term.

Writing a practice plan.

Writing a practice plan and keeping a practice diary is a good idea to ensure that you are:

• Getting into a good routine 
• Ensuring that you are achieving goals based around your SWAT analysis and CPA
• Achieving what you are setting out to do.

There are many practice diary templates out there for you to copy off, I prefer to use pen and paper or a whiteboard which are very visual tools and writing my goals down allows me to absorb the information.

The Musicians Union have a great practice diary you can utilise at any age: https://www.musiciansunion.org.uk/Home/Advice/Education/Resources/Practice-Diaries

Or a practice diary I use regularly with my students which is cheap and great for the younger student.
https://www.musicroom.com/product/mrm013/music-sales-musicroom-practice-book.aspx 

There is no right or wrong way to practice and it often comes down to what your learning preference is, which if you are unsure you can visit the VARK website and answer the VARK questionnaire which will give you a good insight into what your learning style is.
http://vark-learn.com/the-vark-questionnaire/ 

Remember:
It is important to keep a record of how well your practising is going in relation to your career/academic goals and to make sure you are achieving what you set out to achieve.
Success is not a straight line, its a squiggle.