Be Better at Something

Setting goals and taking the steps to achieve them is part of life. You'll need perseverance, determination and focus.

Steps

Identify your goal. It needs to be SMART: specific, measurable, attainable, realistic and timed. For example, "By 30th May, I will be able to solve my Rubik's cube in under five minutes".
Identify the necessary steps. Within the larger goal, there will be smaller targets.
Be patient. Achieving your goals can often take a long time and can be very frustrating. If you stumble, don't worry. Failure is a natural part of learning to do something and should not discourage you.
Take advice. If possible, seek out an independent tutor or course which will help you achieve your goal. The earlier the better: this will prevent you from getting into bad habits from an early stage (particularly important in the case of musical instruments or sports) and will teach you the fundamentals. Once you begin to get the hang of things, you can branch off by yourself. If you want to get better at art, a tutor can teach you the basics. Only you can show your personality and become great.
Be persistent. Anything that is worth doing is never easy. If there was no challenge involved you wouldn't be doing it in the first place. Show your moxie, too. If you keep at it, this something you want to get better at, you'll become great.
Reward yourself.

Stay focused and determined to achieve your goal.
Remember that you can always be better.
Remember there is a reason you're attempting this in the first place. You'll be the bigger, better, stronger person when you're through with it.
Believe that you will be able to achieve your goal.
Never let someone tell you what you can and cannot do.

Make sure it's not something you will regret. Of course you'll be putting a lot of time and energy into whatever you're going to get better at, but decide if you'll regret it before you begin. If you decide while you're carrying out your plan, you may give up. If you give up, you'll get nowhere.