re: If you could rewind the clock and start over...

Unless you are doing it full-time do not try to pick your own stocks. A majority of professional managers don't beat the S&P, you probably won't either. Do not try to time the markets. You may be an outlier that does it successfully, but few are. Max out a Roth IRA annually, preferably spacing out your contributions (actually your purchases) throughout the year. Once you've maxed out the Roth put as much as you can into a taxable account without living in a box and eating vienna sausages every meal. There are mutual funds that do beat the market over time. Pick out 3 or 4 of these weighted towards mid-cap growth and buy monthly or quarterly. Morningstar has a great fund screener. It'll cost you $20 or so for a month of premium access which is more than worth it. When selecting funds look for no-load funds that have beaten the S&P over 5 years, 3 years, and 1 year with a turnover ratio under 25, fees and expenses under 1. Out of the 25,000+ open funds you'll end up with a very short list to choose from. Do not listen to message board stock picks, CNBC commentators, etc. They are useless. Find the best of the best fund managers and let them run your money for you. Review their results annually and re-balance as necessary. As you get older your portfolio needs will change. I'd go for aggressive growth over the next twenty years at least. While doing that you should read up on portfolio management in regard to asset distribution as one gets older.

The most important factor in building wealth in the markets is time. Run some compounding interest scenarios to see what is possible even with small annual returns. Moneychimp has a simple calculator that can be a lot of fun to play around with.

Obviously everyone has different opinions on investing. If I could talk to myself at 25 the above is what I'd recommend.