It would be very invaluable to day traders who would want to take advantage of the difference in prices to make profits.
- Volume on input and output exchanges: To make sure that you will have good prices to buy and sell with your intended money.
- Reputation of exchanges you want to use for inter-exchange tradings.
- Don't store your bitcoin on any exchange after buying it. If you store your bitcoin on exchanges, it should be a very small part of your capital. You should never totally rely on exchanges' reliability and their responses or compensations for customers if there are something seriously wrong with their platforms (hacks, ie.)