1. How to buy altcoins with a credit-card or paypal and with a minimum of hassle?
2. How to hodl (specific) altcoins in the most secure way?
3. How to sell altcoins?
1. If your first priority is to be hassle-free I suggest using
https://shapeshift.io or
https://changelly.com to buy alts. Be careful about the prices and the fees though, they are slighty more expensive than the exchanges.
2. People consider a hardware wallet (like a Ledger Nano S or a Trzeor) to be the safest option, and keeping your coins in a site or an exchange to be the most risky.
3. Either use
https://shapeshift.io or
https://changelly.com, or if you want USD use a good exchange like
https://binance.com to sell them.