The safety methods or the safest way to keep bitcoins are  to keep them in the wallet.
 Desktop Wallet
A desktop wallet offers a number of advantages over an online wallet. While online wallets are easily accessed from anywhere in the world, they are also more vulnerable to potential hacking. Desktop wallets, on the other hand, are accessed only via your private computer, with personal security keys stored just on that machine. Thus, exposure of your security key online is reduced. Nonetheless, desktop wallets are still susceptible to hacks if your machine gets infected with malware designed to root out keys and steal Bitcoins.

Hardware Wallet
More secure than a desktop wallet is a hardware wallet. These wallets are bits of hardware, external devices like USB sticks which you can carry around on your person. An added benefit of a hardware wallet is the complete anonymity with which you can transact. There is no personal information linked to the hardware, so no identifying data which could be leaked. Hardware wallets are resilient to malware, and if you happen to lose the wallet you'll be able to recover the funds using a seed phrase.

Paper Wallet
A paper wallet is also a relatively safe way of storing Bitcoin, although it requires a bit more advanced understanding of how digital currencies work. Generate a paper wallet online using any number of dedicated websites, or generate the wallet offline for even greater security. Paper wallets are stored easily because they don't take up a great deal of space, and they also offer true anonymity: they are simply a Bitcoin seed written in some way on a piece of paper.

Physical Coins
Services are cropping up which allow Bitcoin investors to buy physical Bitcoins. The coin you purchase will have a tamper-proof sticker covering a predetermined amount of Bitcoin. In order to purchase the physical coin, you may need to pay a slight premium over the value of the Bitcoin that you're buying, owing to the cost of the manufacture and shipment of the coin itself.