It's a good idea to have a basic understanding of what you're getting into so you're not investing mindlessly.
Once you've answered the strategic questions above, you'll want to learn the basics of investing: how to read stock charts, etc., and then begin picking some of your favorite companies and analyzing their financial statements. You'll also need to keep up to date with recent news about industries you're interested in investing in. It's a good idea to have a basic understanding of what you're getting into so you're not investing mindlessly.