With all the brokers out there, it can be a very time consuming job to find one that best suits your needs. There are many major factors to consider. Firstly is the cost for each trade. This can vary greatly between brokerage firms. I have seen brokers charge .95 for a trade and I have seen brokers charge 0 for a trade. Most are somewhere in between.
Amongst the cheapest brokers are Zecco and Tradeking. To find out more about zecco, check out this review of zecco. To find out more about tradeking checkout this tradeking reviewed.
Another important factor that may be worth considering is the charge a broker makes for broker-assisted trades. This is when you telephone the brokerage firm and place the trade on the phone. Some stock brokers have no extra fee for this, whilst others charge several times more for trading in this way.
How much money do you have to trade? Do you have enough to satisfy your brokers minimum account size. This is another consideration. Some brokers have no minimum account size whilst others have high minimums that need to be met to have an account.
Now this one I hate the most. Hidden charges. Many stock brokerage frims have fees that are not always obvious. A common charge stock brokerage firms make are inactivity fees. This often a fee charged every 6 month period when you have not made a trade on your account. Fees like these are just plain greedy. I would never use a broker who engages in such practices.
Do you trade on margin a lot? If this is the case, the margin rates could be very important factor for you. They can vary hugely between different brokerages so it probably pay dividends to shop around a bit.
There are many brokers to choose from. Looking at several online discount stock brokers is always a good idea before making your final choice.