Find a good online stock broker and open an account. Become familiarized with the layout and to take advantage of the free trading tools and research offered to clients only. Some brokers offer virtual trading which is beneficial because you can trade with play money (see #9 below). A great tool for comparing online brokers can be found at StockBrokers.com.
If you trade stock regularly, you might find yourself accidentally violating the dreaded wash-sale rule. This means you've sold shares of stock and then bought the same or similar shares shortly thereafter. This can cost you huge tax penalties. With a little planning, you can avoid this fate and still enjoy trading stocks aggressively with a little planning.
Momentum investing usually involves a strict set of rules based on technical indicators that dictate market entry and exit points for particular securities. Momentum investors sometimes use two longer-term moving averages, one a bit shorter than the other, for trading signals. Some use 50-day and 200-day moving averages, for example. The 50-day crossing above the 200-day creates a buy signal. A 50-day crossing back below the 200-day creates a sell signal. A few momentum investors prefer to use even longer-term moving averages for signaling purposes.