Choosing an exchange:
https://www.bitcoin.com/guides/how-to-c ... n-exchange
Mining: I recommend pool mining -
https://www.bitcoin.com/guides/what-is- ... ining-pool
In general, I'd recommend you choose some of the big exchanges, and diversify your holdings so that no one exchange (or wallet) holds all of your coins. For example, Coinbase, Bittrex, CEX.IO, Bitstamp, Bitfinex are all well established brands. But you could pick 2 or 3 of these and spread your coins between all of them, with 2-factor authentication on each.
Mining Bitcoin is not really profitable these days, unless you're going to do it at a huge scale and have access to cheap electricity.