No need to look further, we have big exchanges with high liquidity so no need to look for more. I personally use binance, bittrex and hitbtc.
I list some though these are common things that we should look up to.
• Privacy
• Security
• Liquidity
• 24/7 support
• Instant deposit and withdrawal
For privacy it is logical to use decentralized exchanges than blindly believing to big centralized exchanges.
Security is still main issue and i am really scared after the leak of data that contains hashed emails,passwords,secret questions on coinmama.
Liquidity will increase after bear market.
Support is necessary and big exchanges should implement the system for emergency cases.
I prefer to wait for 3 days if theme is about crypto to fiat transactions.