If you have big volume of bitcoin first of all you want select a secure wallet.There are many wallets in the internet.I Recommended to use if you got big volume of bitcoin use a Hardware Wallets.But it is little bit expensive.But more secure.If you doing some little transaction you can use Web Wallet or Desktop/Mobile Wallets.They are also secure.Main thing is never share your Privet Key with anyone.If You Share you will be get hack and you will lost all of your Bitcoin.