Utilize your financial knowledge, give your answer or opinion to the input question or subject . Answer format is not limited.

Dollar-cost averaging: How often should one use it? What criteria to use when choosing stocks to apply it to?
Dollar cost averaging can be done in a retirement plan, and can be done for individual stock purchases, as this will increase your returns by reducing your risk, especially if you are buying a particular stock for the first time.   How many time have I purchased a stock, bottom fishing, thinking I was buying at the low, only to find out there was a new low.  Sitting with a thousand shares that are now down $3-$4K.  I have a choice to sell at a loss, hold what I've got or double down.  I usually add more shares if I'm thinking I'll recover, but at that time I'd wished I'd eased into my investment.  That way I would have owned more shares at a smaller cost basis.   Anything can happen in the market, not knowing whether the price will increase or decrease.  In the example above a $3,000 loss is equal to the brokerage cost of about 300 trades, so trading cost should not be a factor.  Now I'm not saying to slowly get into the market and miss the bull, like we're having today with Trump, but get into individual stocks slowly, being fully invested in the market.   Also DCA means you do not buy equal number of shares per period, say monthly, but that you buy with the same amount of money a different number of shares, reducing your total costs.  Let's say you spend $2000 on a stock trading at $10 (200 shares), if the stock rose to $20 you would spend $2000 and buy 100 shares, and if the stock dropped to $5 you would spend $2000 and buy 400 shares, by now having amassed 700 shares for $6,000.  On the other hand and in contrast to DCA had you purchased 200 shares for $2000 at $10/share, then 200 shares for $4000 at $20/share, and finally 200 more shares for $1000 at $5/share, you would have amassed only 600 shares for $7000 investment.