Valor
"The better part of valour is discretion."
William Shakespeare
“The courage to take actions in support of one's convictions.”
In the world of UO this translates as challenging evil and defeating it. Basically, just like Justice, this virtue is centered around the Champion spawn system. It allows you to challenge an inactive champion altar and to boost the spawn by 1 red candle once per spawn.
Using Valor
Whenever you come across an inactive champion spawn altar, double click the Virtue gump above your avatar's head on your paperdoll then double click the Valor icon to get a target cursor. Then click on head in the middle of the altar to challenge the champion. You need to be Knight of valor to be able to challenge the champion. Once challenged, a random number of red candles will appear on the altar (between 2 and 4). The champion thus challenged is also totally random unless you challenged a champion specific altar (such as Oaks or one of the dungeon altars). Challenging an altar through Valor will use up a substantial amount of your virtue points. You can therefore only one challenge altar before you need to work up your Valor to knight again before you can challenge another.
Once the spawn is active, you will be allowed to challenge the altar a 2nd time. Challenging an active altar will allow you bump the spawn by 1 red candle, hence speeding up the process. You can only do this once per spawn so choose your moment carefully. Ideally, you should reserve the spawn bumping to the last level as it is usually the most difficult one. In some spawns (like Barracoon) it is advised to use it at the lower level as it is often the slowest while level 4 is quite fast and easy to complete.
Gaining Valor
This virtue is the easiest one to gain. All you have to do is kill monsters around the altar area. A single champion spawn is more than sufficient for you to achieve Knight of Valor. You can gain Valor by killing altar spawn in Felucca, Ilshenar and the Tokuno Islands.