First things first, there is a difference between investing and trading, the former is more for long term while the latter is short (sometimes as short as a few seconds).
Next up, read up online (Investopedia is one good place to start, here also) and offline (books with "asset allocation" subjects). My style is I would try to understand from a broad perspective first, before going down into the nitty gritty.
Then read up on the various portfolios (The Permanent Portfolio, The Gone Fishin' Portfolio, The Bogleheads Guide to Investing, Millionaire Teacher, Rich By Retirement: Invest Smart, Retire Wealthy, etc.). Study their investment strategies and methodologies, and the rationale behind it. You need not follow theirs (mine is a hotchpotch of different portfolio strategies). Find one that is suitable for you.
Then you could go on and read the more academic-practical aspects of the markets (The Intelligent Investor, Random Walk Down Wall Street, etc.).
Do note after reading them, you will find out that everyone's ideas clash with everybody else's and there is no single perfect way. Find one that is suitable for you and implement it.
Cheers.