Regarding your private keys, can either keep them on a software wallet, or on a hardware wallet. The software wallet is the easiest way for beginners, but it implies that you have a computer that is properly secured (strong password, antivirus etc.) and that you do backups of your data. Remember, if you lose your private keys, the money is gone forever. As you get into cryptocurrencies more seriously, you will inevitably look for a hardware wallet, which is a dedicated device resistant to hacking where you can store your private keys (or to say it in an easy way, your crypto assets/invested money). I have already written an article on a hardware wallet, the TREZOR (see here). The most common wallets are the TREZOR and the Ledger Nano S. The TREZOR has a new model being sold from January 2018 (Model T) which will support much more currencies than the current TREZOR. The Ledger Nano S has more integrations currently, but I would recommend to wait for the TREZOR T to judge properly. Those devices usually cost around 100 USD, so once you have more than 100 USD to protect it starts making sense to get one.
For the active trader, execution speed and fill price are very important. I won’t get too in depth here but I have tested many of these brokers and there can be noticeable differences in trade execution times and quality. For the majority of investors, saving a penny per share on a 100 shares order isn’t the end of the world, but for active traders it is something to look into. To understand Order Execution, read this guide.
Investing is a way to set aside money while you are busy with life and have that money work for you so that you can fully reap the rewards of your labor in the future. Investing is a means to a happier ending. Legendary investor Warren Buffett defines investing as "… the process of laying out money now to receive more money in the future." The goal of investing is to put your money to work in one or more types of investment vehicles in the hopes of growing your money over time.
Bonus Stock Market Tip: Everything above is related to how best to invest actively - in other words buying and selling into companies that have been selected by you. But what if you don't have the time, money or inclination? What if the paragraphs above put you off? Perhaps you were looking for a simpler guide? The stock market for dummies perhaps?
If you are literally just getting started, the services offered by most major stockbrokers (information here) as a part of their trading account services will be a good place to start (and free). Firms such as Trade King, eTrade, Charles Schwab and Ameritrade provide a range of online tools. These will give you a feel for how portfolio management software works without having to pay extra to learn. However, these services typically offer no advice (known as execution only), which means that a separate service will be required for information analysis.
Dollar-cost average: This sounds complicated, but it’s not. Dollar-cost averaging means investing a set amount of money at regular intervals, such as once per week or month. That set amount buys more shares when the stock price goes down and fewer shares when it rises, but overall, it evens out the average price you pay. Some online brokerage firms let investors set up an automated investing schedule.