Before deciding where to allocate your investments, it’s critical to think about your long-term and short-term goals. It’s important to know how much risk you are willing to accept. As you approach retirement, fixed-income securities, such as highly-rated bonds and money market accounts, offer a greater level of safety. But a younger investor might want a more high-risk, high-reward strategy for at least part of their investments to maximize returns over a long period of time.
1$0.00 commission applies to online U.S. equity trades, exchange-traded funds (ETFs), and options (+ $0.65 per contract fee) in a Fidelity retail account only for Fidelity Brokerage Services LLC retail clients. Sell orders are subject to an activity assessment fee (from $0.01 to $0.03 per $1,000 of principal). There is an Options Regulatory Fee (from $0.03 to $0.05 per contract), which applies to both option buy and sell transactions. The fee is subject to change. Other exclusions and conditions may apply. See for details. Employee equity compensation transactions and accounts managed by advisors or intermediaries through Fidelity Clearing & Custody Solutions® are subject to different commission schedules.

The best way to practice: With a stock market simulator or paper-trading account. Many brokers offer these virtual trading platforms, and they essentially allow you to play the stock market with Monopoly money. Not only do you get to familiarize yourself with trading platforms and how they work, but you also get to test various trading strategies without losing real money. The link above has a list of brokers that offer these play platforms.

C (Fair) - In the trade-off between performance and risk, the stock has a track record which is about average. It is neither significantly better nor significantly worse than most other stocks. With some funds in this category, the total return may be better than average, but this can be misleading since the higher return was achieved with higher than average risk. With other funds, the risk may be lower than average, but the returns are also lower. In short, based on recent history, there is no particular advantage to investing in this fund.
While it doesn’t offer as much for beginner traders and new traders, you could host a family office or business portfolio on TradeStation with no problems. In fact, its tools are so good it sells many of them for a fee to professional investors with accounts at other brokers. With an active account at TradeStation, you get those tools for free. Just beware the minimum $2,000 balance or five trades per year to avoid a $95 annual account fee.

Every investor should try to establish what their goals and objectives are prior to investing. There isn’t necessarily a wrong objective, but it’s more important to understand your goals because that will help drive your decisions. For instance, if you plan to regularly trade in and out of stocks, you might be better off opening an IRA account so you don’t have to pay taxes on your trades. If you plan to be a long-term investor, taxes won’t be as important of a factor and you could hold your account in a taxable or tax-free account.

NerdWallet's ratings for brokers and robo-advisors are weighted averages of several categories, including investment selection, customer support, account fees, account minimum, trading costs and more. Our survey of brokers and robo-advisors includes the largest U.S. providers by assets under management, plus notable and/or emerging players in the industry. Factors we consider, depending on the category, include advisory fees, branch access, user-facing technology, customer service and mobile features. The stars represent ratings from poor (one star) to excellent (five stars). Ratings are rounded to the nearest half-star.
By knowing how much capital you will need and the future point in time when you will need it, you can calculate how much you should invest and what kind of return on your investment will be needed to produce the desired result. To estimate how much capital you are likely to need for retirement or future college expenses, use one of the free financial calculators available over the Internet.

Astute readers will realise that the above guidance is mainly taking different angles to help prepare for and guide decision making by the investor. The ability to confidently make decisions is vital for investment profits and long-term success. This pdf about the decision making models of Charlie Munger (business partner to Warren Buffett at Berkshire Hathaway - both are certified investment immortals) is almost certain to prove helpful.
For online platforms, websites give the user options and availability of the stock he wishes for, across all the platforms available. If he places an order, it gets stored in a database. After the confirmation of the trading account and payments, the order gets forwarded and the user gets his stock, in the form of money, transferred to his trading account.