Method #1

There is always a difference in price between exchanges.  Use this to your advantage by buying a coin on one exchange and selling it on another exchange.  Also if you are looking to buy a coin for purchasing something try to find the best price across all these exchanges. 


A few of the top exchanges:

OKCoin
BTCC
Cex.IO
BitFinex
Gatecoin
Poloniex
Bittrex

Method #2

Just like there can be price differences across exchanges, trading different pairs of coins could result in varying amounts in the end.  Using this you can make huge profits with almost any currency.

Example:
Start with 1 USD
USD/BTC → BTC/LTC → LTC/USD
End With 1.01 - 1.03 USD
Repeat


Method #3

Using CoinMarketCap.com find a few altcoins with:

Price Below $0.01
Market Cap Above $100,000
Available Supply Below 40,000,000
Volume Between $500 - $1,000
Rising Price

Then spread your money across the coins, wait a week or two and sell them. More than likely at least one altcoin will rise in price making up for the others if they don’t.

Method #4

Find a coin that's rising in price over the past month at CryptoCoinCharts.info

Buy some of the coin
Wait and Monitor the Price for a few days to a few Weeks
As the Price Rises if it Starts to Fall Sell
Profit


Summary

Depending on your personal preference and the opportunities you find you can make a huge profit with these methods.  Though at certain times one method will be better than another.