Understand that you are starting a lifelong journey. Commit to being open-minded and flexible. Your goal is to start on a path of personal growth that will evolve and mature as you experience life.

Start reading and learning. Stick with what interests you and try to get a sense of the big ideas that philosophers are concerned with.

Choose a type of philosophy. Philosophical thought is organized around many types of philosophies including: axiology, ontology, aesthetics, epistemology, ethics, logic, metaphysics and political theory. Follow your interests. Feel free to choose more than one type because you see particular linkages. You will enjoy thinking through how to meld them successfully.
After deciding a philosophy type, learn the background history of your chosen philosophy, including readings from the key philosophers. Understand the key questions that were addressed and get a solid understanding of the key concepts.
Improve your basic understanding of other types of philosophies. You cannot be an expert in everything but recognize that there is great value in understanding the basics of what others have done. A broad understanding of what people are struggling with and what the discussions have been about will help you to develop your own personal philosophy. Feel free to learn and build on existing ideas. It is difficult starting from scratch, so why not take another philosopher's ideas as a basic framework to get started? Many well known philosophers started like this. For example Plato took the undoubtedly oral and sociable Socratic method from the real Socrates, and used it as the basis for his highly polished literary Socratic method, which in turn was taken by Aristotle to form the basis of Logic particularly syllogisms.

Expand and evolve your thinking. The framework you have selected is a starting point. As you experience life, test it out and see what works for you and what doesn't. When you have time analyze this and refine your framework philosophy. Over time, as you solve problems and assess the quality of the decisions you have made, you will be able to evolve from where you started into something autonomous of the original philosophy.
Become a critical thinker. Keep track of where you have obtained the basis for ideas, tenets, theories, etc., in your new philosophy. Being able to trace your theorizing or conclusions back to their source will help you defending your ideas or pushing them further. Very little develops in a vacuum.
Referring to what other philosophers have said gives your philosophy greater credibility because you are displaying your depth of knowledge and understanding of existing philosophies.

Be patient and allow your ideas to percolate over time. When you have spare time, analyze the framework of your nascent philosophy, and try to find problems and solutions. Taking the development of your philosophy gradually will allow it to evolve into something autonomous of the original philosophy.
Keep a journal and continue writing down your thoughts and ideas, even if they're not coherent. Patience is essential because it may take you years to sort through all the discarded notions to find the treasure buried underneath. The passage of time is healthy, as it allows your ideas to keep evolving and to be tested by daily events.
Ask some pertinent questions, such as:
What is the purpose of your philosophy? Do you want to apply it to all of society or just a sector?
What is your role in your philosophy? What, if any, are the roles of particular people in your philosophy?
How will you explain the basis of your philosophy to others? Is it helpful on a practical level, or Utopian?
How do other belief sets or philosophies fit in with or go against your philosophy?
Are you willing to write down a thesis or book of your philosophy? Or would you rather write stories that contain your philosophy but are not overtly a philosophical work in structure?

Talk to others interested in philosophy. They can point out faults you might have missed and give different solutions. This is helpful for developing your philosophy.
Join a local philosophy group, club, or chapter.
Join an online group that has private forums where you can share your ideas freely and get responses.
Visit your local university and ask to speak with philosophy professors to share your thoughts with them.
If you find someone else who really understands where your new philosophy is headed, embrace their enthusiasm but take care to keep working on your understandings separate from their enthusiasm. It is hard to follow someone else while they are still working out what it is that they believe, so their enthusiasm may just be because they like and trust you.

Actively find/seek out new experiences to help you to see things in different ways and from different angles.
Keep an open mind.
Learn to accept criticism and grow from it; it might just help strengthen you and your philosophy.
Always have a pencil and a notebook to note down ideas as they occur to you, or you come across them.

Keep reading philosophy. It will allow you to see previous philosophers' attempts, what they found, and what fallacies they fell into; thus, progressing your own philosophy. This will also help you to see whether or not you are attempting something that a previous philosopher has already tried. http://www.goodreads.com/list/show/451.Best_Philosophy_Book

Keep up to date with the world. Try reading a newspaper once in a while. It'll help you apply theories to real situations.
For example, take a serious news story that involves issues impacting on many sectors of society and ask yourself: "What would I have done?" Work your answers into your developing philosophy to see if it can withstand actual events and provide explanations, instruction, or greater understanding.

See yourself as a philosopher, whether or not you work as one. A career in philosophy, or similar roles such as a researcher in a think-tank or institute, will ensure you dedicate regular time to your philosophy, but for the part time philosopher make sure you dedicate enough time to it so you keep improving and don't forget bits of your work.

Try as much as possible to live up with your thoughts, even when you are experiencing something uncanny that probably distracts your opinions,get back to those notes that you have made about your philosophy or the inspiring books that you have been reading. It'll help.