Your climbing shoes should always be comfortably tight. Make sure your toe knuckles are flat and comfortably curved while you wear them. Also, it is best to have a snug fit around your heels. While many tend to think it is better to start with painfully tight climbing shoes, it is not the best practice. Imagine having constant pain in the foot while you try to hover over a steep crag. It surely does not sound like the right idea.