To buy shares you need an account with a broker: a bank or an online investment platform that is allowed to send orders to the stock exchange and that keeps the shares you buy in a custody account in your name. Opening one usually takes a few minutes online and requires proof of identity.
What to compare
Brokers differ mainly in cost and in what you can buy. Look at the commission per trade (often a minimum amount plus a percentage), currency exchange fees when you buy shares listed abroad, any monthly or custody fee, and which exchanges and funds are available. For small, regular purchases the minimum commission and currency fees often matter more than the headline percentage.
Ordinary account or a special savings account
Many countries offer special investment or pension accounts with different tax rules or limits on how much you can deposit. Which one suits you depends on the rules where you live and on when you need the money - check your local tax authority or an independent adviser before choosing.
Safety
Choose a broker supervised by the financial authority in your country. Your shares are normally held separately from the broker's own money, but rules on investor protection differ between countries. Never let anyone else open or run an account for you, and be wary of platforms that promise guaranteed returns.
This content is general information, not investment advice.