Breaker contacts should look fairly new even after years of service. Why? Because with properly aligned contacts, the only time severe damage should occur is when the breaker operates under load.
Before manually operating a breaker, methodically shut down all connected loads. Ideally, you will open a breaker only when there's no current flow across its contacts.
Of course, contact surfaces aren't perfectly smooth, and you don't get 100% contact between all surface points on the respective contacts. Some arcing will occur, and over time the surfaces will become pitted. You can typically recondition (by filing or sanding) the contact faces. Make sure you take photographs before and after filing.
But consult the breaker manual before reconditioning; there should be a specification on how thick the resultant contact must be. If you can't make that spec, replace the contacts.