Before we invest we need to make sure that we have a big patience because the market is unstable, and not all the time we will earn, altcoins are not the same they have different function and they have also different market cap and different supply, so there is no way to track when the particular alt coin rise, but mostly they will rise when the market is bullish and they always follow the btc trend based on the past experience.
With few exceptions Alt coins are risky, they have the capability to wipe out your entire investment within few days. A good example is the Trump Coin, it came in the name of current US president and there were expectations that it will go further high but after 2 to 3 days of its launch it starts falling till date.
Alts must be for short duration i.e. you invest, take profit and quit. Don't think that Alts have fundamentals like Bitcoin and they will go up after sometime. There are very few Alts that have survived so far for more then 5 years, mostly they have a short life. Moreover, it's important that what alts you have chosen for investment. People buy cheap coins with greed of getting more profit on low investment and that never happened.
These few points must be kept in mind before you invest in Alts, otherwise you will end up your money getting struck.