Choosing a business or brand name

1. What sorts of business names are there?
2. What are the main considerations when choosing a business name?
3. How can I find out if someone else is already using the business name I want?
4. I searched and didn't find anything. Presumably that means I am OK?
5. I found a similar name to the one I want, but I'm still keen to use it - is there any way round it?
6. If I go ahead anyway, what's the worst that can happen?
7. Do I need to register my name as a trade mark?
8. Can I register any name as a trade mark?
9. Should I choose a business name that I can register as a domain name?
10. Do I need a name I can register at Companies House?
11. Are there any words I can't use in my business name?
12. What if someone copies the name I choose?
13. The business is going to trade abroad - are there any special considerations?