I was recently studying this question and here is what I found:
- You can use Coinbase if you are in US and you will feel pain because of their fricking commissions
- You can use some exchanges like Bitfinex, Bittrex and some others but still the rate would be awful
- You can use new platforms like Cryptology and some others but there is no information on them atm but there might be the better rate
- You can use LocalBitcoins (which is banned in Russia)
What is your choice?
Localbitcoins, atms, sell to your friends, bitstamp has an interesting thing where you can withdraw in gold, and there is no tax on gold. Recently in croatia there was two bitcoin stores opened where you can take 2000 euros in cash without submitting id, thats also nice