Let's look at the wallets for altcoins and in particular for Ethereum. However, before you start reading this, you first have to read
How to store Bitcoin? Creating a Bitcoin wallet.
Official Ethereum Wallet
You can download the official Ethereum Wallet on the official Ethereum website or on github. This is a heavy client and will take 28GB on your computer. But frankly, I wouldn't bother with it. It's crap. I used it a bit over the past few months and these are my thoughts:
1. I couldn't download the full blockchain on my computer once. I have a very typical SSD, so this shouldn't be a problem, but I tried at least 5 times and each unsuccessful attempt took more than 24 hours.
2. On 2 out of 3 computers the wallet is so resource-intensive that you can't do anything else whilst it's running.
3. After 2 hours of keeping the wallet offline, a sync, to get the latest blocks, could take 20 minutes! In contrast, Bitcoin Core syncs in seconds.
4. Once my computer froze when the wallet was open. After the restart, the wallet simply stopped working. I had to delete it and download it again in order for it to start working again.
I get it, Ethereum is super cool and everyone likes it because of that, but their official wallet is a joke.
Saying that it still has a few advantages:
1. It supports multiple wallets
2. The wallets are stored as encrypted files which you put a password on when you are creating them. If you don't set a password - you can't do anything with the wallet.
3. Each new wallet has a new icon. It helps you check if the address of the receiver is correct.
4. You can check your balances and send cryptocurrencies to other addresses.
MyEtherWallet
https://www.myetherwallet.com is an online wallet which connects the nodes to their own servers (or any other servers for that matter). An important note about it though. Be careful about its counterfeit versions. Read this post about how someone I know lost 2ETH.
MyEtherWallet is probably one of the most popular wallets out there. It's very friendly and doesn't store your keys. Every time you use MEW (MyEthereWallet) you load up your keys and input your password.
MEW works with hardware wallets and in fact, recommends using them to store your private keys. Read more about hardware wallets here.
Conclusion. If you aren't paranoid and carefully check that the address of the website you are visiting is actually correct - MEW and a hardware wallet (or an encrypted USB) with the wallet file will be perfect for you. If not, the official wallet is the way to go. Just remember that it is not very good and it'll most likely take you a few hours to just get started with it.
MyEtherWallet is also good to manage other cryptocurrencies which use the Ethash algorithm. For example, ETC, EXP or UBQ. By the way, if you know the node address you can also point the wallet there and manage other cryptos that use the same algorithm.
Litecoin wallet
LTC Core is an official Litecoin Wallet which was developed based on Bitcoin Core. That means the wallet is heavy, but its size is only 10GB.
Don't have 10GB free? Then you can use Electrum for LTC.
If you are storing a small amount of a large number of cryptocurrencies - you will find Jaxx to be most useful.
Dash wallet
Dash Core is an official Litecoin Wallet which was developed based on Bitcoin Core. That means the wallet is heavy, but its size is only 4GB.
Don't have that much space? Then you can use Electrum for Dash.
If you are storing a small amount of a large number of cryptocurrencies - you will find Jaxx to be most useful.
Ripple wallet
Ripple doesn't support their official wallet. However, there is a branch which separated from the official wallet called Rippex.
Please note that Ripple takes around 20XRP (around 19USD as of 03/03/18) for the creation of a new wallet.
You can use a service for generating a new paper wallet here. However, please use it with caution. No one knows what kind of data those services store and who might have hacked them.
TL;DR
I would recommend storing your cryptocurrencies in the "coldest" place possible. Encrypted offline files will never get accidentally flashed or exposed online. If you have the money, buy a hardware wallet or at least a new USB and encrypt it.