After you have setup a trading account and transferred funds, it is time to get started. Initially trade with very small amounts about a a few hundred dollars. There are various types of orders and it is very important to understand how and which ones to use.
e.g. Buy 100
Buy and sell at market price. Never ever use this type of order. Only in cases of when you have to sell in panic or trading long term and dont care what price you pay. If you are starting then it is ok. You can use market for both buying or selling.
e.g. Buy 100 APPL at 110.5
e.g. Sell 100 JPM at 41.5
When buying it means, I will not pay more than the limit price e.g. 110.5. You will be guaranteed that your order is filled at 110.5 or lesser or it does not get filled. For selling it means that i will not sell for a price lesser than my limit e.g. JPM not less that 41.5. Limit order is what one should always use. Be patient and get at the lest price you can get when buying. You can use or bar 1 minute chart if you are a day trader or a 60 minute chart if you are a few weeks trader or longer trader to decide the price to put limit on. Just make sure its not too low that you never get filled.
e.g. Sell 100 APPL at 105.5
This order means if the price touches 105.5 sell at market value. Stops are very important and act as protection against massive losses. When ever you buy stocks put a protective stop loss, so your damage is always limited to a certain amount.
e.g. Sell 100 APPL at 105.5 with limit 105.5
This order means if the price touches 105.5 sell but till i get atleast 105.5 . Its a stop with the restriction of a limit. The order might not get filled if the price is falling sharply as your limit might not get filled. So either keep the limit lower that the stop or use a Stop Market.
In summary buy with a limit order and always put a stop loss of a certain percentage or a couple of Average True Ranges.