Everything Hodedofome said is excellent.
For myself, how I got started was this: I read the book "Stocks for the Long Run" by Jeremy Seigel. Around the same time I came back from a deployment and had about 23k in my bank account. I opened a TD Ameritrade account and put ~10k into SPY, this was around 2008. As the years went by, I worked on several books(Peter Lynch, William Bernstein, Millionaire Next Door, a couple frugality/minimalism books) and I watched Mad Money a lot and read through SeekingAlpha and Fool articles. I also subscribed to the Income Investor Motley Fool portfolio.
By 2012 I had formulated a mostly DGI/value strategy, but with a little bit of rulebreaking. I like the consistency of dividends, the steady growth, the downside protection(goes for value stocks too).
For the rulebreaking, I'm interested in special events, in companies that don't meet traditional metrics(like DGI investor's 5+ years of dividends/growth, semi-recent cuts in dividends, etc). BAC(Bank of America) when it went to ~5$/share in 2011, and the future of that stock. NOK(ia) when it was trading ~2-3$/share and had the Lumia coming out(dumped it when they sold phone division to MSFT), SIRI(usXM) for their continued capital return plan(buybacks buybacks BUYBACKS!) and their FCF.
When my current plans pan out over the next ~2 years, unless I see a place I'd specifically like to put my money, I plan on index'ing most of it back up. Of my 18k ROTH, 6k is a CD and 3k is VIG(vanguard), so only half of that is "actively" managed, but by actively managed, I've bought and sat on stocks(SIRI, SNA(Snap-On), INTC. And plan on doing that for a very long while. My 401k is about ~35% of my net worth, and it's all indexes.
Active management is an addiction I can't say I'm all that happy to have, and I wouldn't recommend it. Until the recent run up in INTC, I was lagging the S&P from 2013-2014 by about 15%. I'm not sure if I broke that difference with that one move, but the research is pretty damning, I'm likely to underperform the market. I believe I sleep better at night knowing specifically why I own 'X' company, instead of why I own 'Y' Index, and I enjoy following things, but try and limit your exposure to your own choices.
I recently got options approved on my account, and bought a couple of out of the money LEAPs.