MyEtherWallet tells the user:
You need to back up your private keys externally and verify you can access the wallets.
I am wondering, how do you verify you can access the accounts without compromising (e.g., importing into geth) the private keys on the cold storage?
There are a few different reasons for verifying your key.
To make sure you actually saved the private key and address correctly. e.g. You saved a private key but recorded the address 0x122... instead of 0x123... (note: you should avoid hand writing things anyways).
To make sure you have all the necessary information, including the password. e.g. You thought you typed password but you actually typed passwordd. e.g. You saved the public key and password but not the private key. e.g. You saved the keystore file but then opened it in Microsoft Word and now it's corrupted.
To make sure the software you used derived the correct private / public key pair.
For the first two items:
You can simply ensure you can access the wallet via the private key or keystore file and (1) make sure it unlocks (2) make sure the address matches what you have recorded. On MyEtherWallet, you can use any of the other tabs to do so: View Wallet Info, Send Transaction, Digix, or DAO. If you are able to access the wallet without errors and the address is the same, you're golden.
The third item is a bit trickier. You can either:
Use a different library to access the wallet and make sure the public / private pair is the same as what you have recorded. By library, I mean a different programming language / client. So, with MyEtherWallet you would want to verify with a non-Javascript library, like geth (Go) or parity (Rust) or c++ (eth). These can be a bit tricky to install in a cold storage environment so...
Send a small amount of ETH to your new wallet. Then send that small amount back out using the Offline Transaction tab. If your transaction successfully arrives and leaves your wallet you can ensure you have a private key that accesses the address you saved, and you can both successfully send and receive ETH at that address.
Remember:
When making backups and verifying backups, always verify what you saved via where ever you saved it and, ideally, wherever it is going to be stored. It does you no good to copy the address from MyEtherWallet -> Text Document -> MyEtherWallet again. Instead copy all info to a document / folder. Then copy/select it from that location and attempt to access via MyEtherWallet.
Always make multiple backups. Please. Saving it on your hard drive does nothing if your HDD crashes. Saving it on a single piece of paper does nothing if your house burns down. Etc.
Take your time. Practice if this is a new experience for you. Do the entire process and then do it again until you are comfortable and confident. You can make as many wallets as you want, just make sure you don't get them confused!
