1) You can start with small sums of money
2) Try to always minimize your costs (comissions, taxes, etc).
3) Routine investing (dollar cost averaging) pays off. No question about it.
http://www.dripinvestor.com/
You can buy stocks direct from the the company's transfer agent. It works pretty much like a savings account only the small amount you put into your "savings" account goes into a share purchase (typically monthly). Costs are low so more of your money goes to work for you. Some of these plans are even free!
I've been a dividen reinvestmen plan investor for 14 years now. It is one of the BEST financial decisions I've ever made. Smalls sums really do add up to large sums over time. There is no better time than today to start.