The Norse Viking concept of bad wasn’t so black and white as many people nowadays tend to think. It is more the idea of someone either being in frith with their family/tribe/group, vs going too far and being too wild in their actions and being outlawed and considered dangerous basically. Loki is a good example of this. He isn’t evil really, just sort of one who was all about testing the limits of social order and bringing in new ideas. For a long time he was a mix of both positive and negative in regard to his value to the Aesir, until he eventually went too far and also by this taunted his wyrd to go down a darker path that threw him out of being in frith with the Aesir. Norse concepts of right and wrong and righting wrong are more about balance and restoring balance, than about moral judgment or condemnation, which is a Christian cultural influence and way of thinking. Sadly many Heathens are still far too tainted by Christian thinking and this creates a environment of discord and a general lack of frith in the Heathen scene in general. Generally speaking proper Heathen way of thinking is very open minded and accepting that others outside ones family/tribe/group will have different ways of thinking. The greatest value for historical heathens when it came to actions was to take actions that upheld the frith within their family/tribe/group. Even frith between groups was important as addressed by the codified system of weirguild, and addressing actions with similar counter actions when actions throw out of balance frith. A good example of how what is considered proper differs between each family/tribe/group is that for the Vanir it is considered proper and normal for sisters and brothers to have sex with each other, and even the Aesir do not judge the Vanir for doing so within their own group as they see that as what is proper Vanir behavior, but the Aesir would not allow that kind of behavior by members of the Aesir as that is not proper Aesir behavior. This concept of differences of what is considered proper behavior I feel also applies with regards to those who follow different gods or goddesses as their patron. Like what is proper behavior for an Odin follower, I feel is not the same as what is proper behavior for a Tyr follower, or a Freyja follower. I feel that this concept of proper behavior for each depending on whom they connect with spiritually applies not only in regards to types of actions not allowed or considered taboo, but also in regards to types of behaviors that should be done. For example Odin followers should be into runes and should study magick, and a male follower of Odin having sex with women outside of his marriage (so long as his wife is ok with him doing so) is also acceptable as that is part of honoring the ways of Odin. One who follows a god or goddess that has a more strict code of conduct has to be more strict about their actions and behaviors as this reflects the values of the god/goddess they follow. Acting in ways that respects the value of the god/goddess you follow is the act of staying in frith with your patron and respecting the concepts they stand for. Of course I feel that when you are part of a group you should honor the rules the group has for actions when dealing with the group, it’s members, or doing any activities which represent the group; this is staying in frith with the group. Staying in frith with your group as well as with your patron god/goddess is very important I feel. Actually it would be considered more worse in the Norse concept of morality to harshly judge others as this is harmful to frith. Unless the other person is directly living within your family/tribe/group it would be considered wrong to judge someone else unless that person takes some action which causes harm to your family/tribe/group/friends/allies/gods/goddesses. judging others without cause is actually harmful to the frith of your own family/tribe/group/friends/allies as that invites conflict that often times will have a negative impact on all those you hold troth with. The most important thing for proper actions in all cases is to act in ways that uphold frith, honors your troth connections with others, and upholds any oaths you have made. If you keep in mind these three things then you should be making the best possible actions for all situations.

This is what Wikipedia has to say about frith:

Frith is an Old English word meaning “peace; freedom from molestation, protection; safety, security”.

In terms of Anglo-Saxon and post-Anglo-Saxon culture, the term has a considerably broader scope and meaning. Frith has a great deal to do not only with the state of peace but also with the nature of social relationships conducive to peace. Moreover, it has strong associations with stability and security.

The word friþgeard meaning “asylum, sanctuary” was used for sacrosanct areas. A friþgeard would then be any enclosed area given over to the worship of the gods.

Frith is also used in the context of fealty, as an expression of the relationship between a lord and his people.

Frith is inextricably related to the state of kinship, which is perhaps the strongest indicator of frith. In this respect, the word can be coterminous with another significant Anglo-Saxon root-word, sib (from which the word ‘sibling’ is derived) – indeed the two are frequently interchanged. In this context, frith goes further than expressing blood ties, and encompasses all the concomitant benefits and duties which kinship engenders.

Frith also has a legal significance: peace was effectively maintained in Anglo-Saxon times by the frith-guild, an early manifestation of summary justice.

Wikipedia page about frith

Troth means loyalty to all those you hold relationships with. Loyalty means to stay by them and to maintain a tie with them and to keep any promises you make towards them.

Here is an online defination of troth:

troth
/trôTH/
Noun

1. Faith or loyalty when pledged in a solemn agreement or undertaking.
2. Truth.

Synonyms
fidelity – faith – allegiance – faithfulness – loyalty

This concept of faithfulness does not mean sexual faithfulness _unless_ it has been specifically agreed that this is part of what it means between both parties. For example Odin is marries to Frigga, yet he has many lovers. He would never consider wishing to leave his marriage to Frigga or having a greater overall connection to other women than he does to her. His other sexual interactions are kept in the context of being not something that competes with the unique relationship he holds with Frigga. Many of the Norse gods/goddesses have sex with others outside their marriages. For some of them this is alright as that is part of the agreed or implied arrangement for those relationships. As well some of the gods/goddesses are sexually monogamous. This really depends on what is the agreed relationship.

Merrian-Webster definition of troth
Freedictionary definition of troth

As you see part of troth is also to keep ones word. Most important is to uphold oaths. Oath breakers are the one type of person in the concept of Viking Norse culture that are totally unforgivable; at least those who intentionally break oaths. Those who purposely break oaths with intention to cause harm are called nithlings and are considered to be worth less than dirt. What this means is that it is important you keep your word. Of course if something happens that you cannot keep your word then you need to own up to this and talk about it with the ones you made the promise to and see if another arrangement can be agreed upon. Keeping ones word does not mean being a inhuman robot, sometimes circumstances do come up that don’t allow someone to keep their word, the point is that the person does their best and communicates with the others involved when they cannot and is responsible for their actions in this way.

In modern heathenism there is something called thews, this it a codified set of principles that it is considered good (by some people) to follow. None of the existing modern thews are actually something written down as principles that one should or has to follow, from the Viking times. They are all modern creations. Many of them are good ideas (at least for some people). The most popular thew in current day Heathenism is the Nine Noble Virtues, but this is not the only one. There is others such as the Anglo-Saxon related Heathenism one called the The Twelve Æþeling Þews. There is also a very nice one associated with the Vanir, the Vanic Virtues (the one I personally follow). None of these thews are in any sense required for anyone to follow who is Heathen. Like mentioned earlier the only basic principles that must be followed by everyone is respect for frith, troth, and keeping oaths (ones word). Really as was discussed earlier, if one does or does not follow one of other more than one of these thews or some other thews of guiding principles should be determined by what agreements any groups you have troth with wish, in combination with and most important of all; what your patron gods/goddesses wish you to follow. For those not connected to any Heathen group than following what your patron gods/goddesses wish is the only factor that matters in deciding which, if any, of the lists of thews is right for you to follow.