So for me I will buy some altcoins and wait for it to pump before you sell it, if you are a ahort term trader just choose the altcoins that are very active from pump and dump.. But if youre a long term type of trader then set your sell up to 100% of profit from your buying price. It defend on your choice but the most important one is to gain and not to loose.
if you're a daily trader maybe you'll do more sales, probably when the price has exceeded the price I bought earlier, then I would think to sell but that depends on the market conditions if marketcaps keeps growing I will hold it until the price stops rising then I will sell it, for long-term investments. I think you should set a target price you want to achieve, target price to your liking,,