My biggest concern is that there are so many exchanges. How the heck do I know which ones will pay me after I make an exchange? I know I have to check their reserve balance, but what else should I look for?
If i may suggest that you trade BTC and ETH on your local exchange site, it's better if you know about it, don't trust the exchanges out there too much, a lot of exchanges these days lead to scams.
Exchange sites, generally the same as buying and selling and profit, there are different systems such as: Margin, Futures, Spot, fiat and so on, the point is: you must have trading knowledge.
Before you trade on the exchange site, try to visit here:
https://bitcointalk.org/index.php?board=223.0, You will know the exchange's good and bad reputation, before you proceed to trade.