If you have a job, your employer may offer a 401k or 403b retirement plan as part of your benefits package. These accounts invest your money for retirement, but your investment options are limited to the choices provided by your employer and plan provider. If your employer doesn't offer a retirement plan, you can open an IRA on your own with your bank or brokerage company.
By understanding your risk tolerance, you can avoid those investments which are likely to make you anxious. Generally speaking, you should never own an asset which keeps you from sleeping in the night. Anxiety stimulates fear which triggers emotional responses (rather than logical responses) to the stressor. During periods of financial uncertainty, the investor who can retain a cool head and follows an analytical decision process invariably comes out ahead.
Define and write down the conditions under which you'll enter a position. "Buy during uptrend" isn't specific enough. Something like this is much more specific and also testable: "Buy when price breaks above the upper trendline of a triangle pattern, where the triangle was preceded by an uptrend (at least one higher swing high and higher swing low before the triangle formed) on the two-minute chart in the first two hours of the trading day."
Buy in thirds: Like dollar-cost averaging, “buying in thirds” helps you avoid the morale-crushing experience of bumpy results right out of the gate. Divide the amount you want to invest by three and then, as the name implies, pick three separate points to buy shares. These can be at regular intervals (e.g., monthly or quarterly) or based on performance or company events. For example, you might buy shares before a product is released and put the next third of your money into play if it’s a hit — or divert the remaining money elsewhere if it’s not.