1. Your necktie can be darker than your shirt and your shirt can be lighter than your suite. A necktie can also contrast it as well.
2. The more color you wear, the more difficult you coordinate them.
The best rule will be to observe more other people's dressing. Looking at their combinations, you can ask yourself some questions. Do they look great with those combinations? If there is a message you get from that combination, what will it be? You can learn from them.
Necktie is one of the forms of self-expression a man has. If you dress based on what you learn and feel comfortable, and if you hear some negative comments about it, you can tell those guys that you are a good dresser. Remember confidence comes from being able to make the right decision, not having it made for you.