Long term investment for money
What explains the most of the future returns of a portfolio is the allocation between asset classes. In the long term, stock investments are almost certain to return more than any other kinds of investments. For 40+ years, I would choose a portfolio of 100% stocks. How to construct the portfolio, then? Diversification is the key. You should diversify in time (don't put a large sum of money into your stock portfolio immediately; if you have a large sum to invest, spread it around several years). You should diversify based on company size (invest in both large and small companies). You should also diversify internationally (don't invest in just US companies). If you prefer to pick individual stocks, 20 very carefully selected stocks may provide enough diversification if you keep diversification in mind during stock picking. However, careful stock picking cannot be expected to yield excess returns, and if you pick stocks manually, you need to rebalance your portfolio occasionally. Thus, if you're lazy, I would recommend a mutual fund, or many mutual funds if you have difficulty finding a low-cost one that is internationally diversified. The most important consideration is the cost. You cannot expect careful fund selection to yield excess returns before expenses. However, the expenses are certain costs, so prefer low-cost funds. Almost always this means picking index funds. Avoid funds that have a small number of stocks, because they typically invest only in the largest companies, which means you fail to get diversification in company size. So, instead of Euro STOXX 50, select STOXX 600 when investing to the European market. ETFs may have lower costs than traditional mutual funds, so keep ETFs in mind when selecting the mutual funds in which to invest. For international diversification, do not forget emerging markets. It is not excessive to invest e.g. 20% to emerging markets. Emerging markets have a higher risk but they also have a higher return. A portfolio that does not include emerging markets is not in my opinion well diversified. When getting close to retirement age, I would consider increasing the percentage of bonds in the portfolio. This should be done primarily by putting additional money to bonds instead of selling existing investments to avoid additional taxes (not sure if this applies to other taxation systems than the Finnish one). Bond investments are best made though low-cost mutual funds as well. Keep bond investments in your local currency and risk-free assets (i.e. select US government bonds). Whatever you do, remember that historical return is no guarantee of future return. Actually, the opposite may be true: there is a mean reversion law. If a particular investment has returned well in the past, it often means its price has gone up, making it more likely that the price goes down in the future. So don't select a fund based on its historical return; instead, select a fund based on low costs. However, I'm 99% certain that over a period of 40 years, stocks will return better than other investments. In addition to fund costs, taxes are the other certain thing that will be deducted from your returns. Research what options you have to reduce the taxes you need to pay. 401-K was explained in another answer; this may be a good option. Some things recommended in other answers that I would avoid: