Highlights. I think highlights should be natural looking. It should be like if you've been in the sun, at the beach for three months, and you know how the sun will make your hair lighter. Highlights are all about giving contrast to your hair and dimension. So I think the highlights should always be a little bit more around the face and a little bit more towards the end of the hair. You don't need to do highlights from the roots all the way down. You don't need to do highlights where, for example, part of your head is never going to show. You're never going to show anybody your highlights here. So why do it?
You should keep it as natural as possible. It should be one shade, two shades, three shades lighter than your natural base.
Don't forget also, highlights you should do a few on your outside hairline when you wear your hair up, because otherwise it will be darker here. Make sure you get a few highlights on the back of the head.
Highlights will definitely dry your hair a little bit. You probably need to do a lot of conditioning treatment and get some haircuts and take care of your hair, because it will definitely dry your hair a little bit.
If you have fine hair, highlights might actually give you more body to your hair. It might add fullness to it. It's also an option to actually get your hair fuller. Like I said, you don't want to overdo it. So the more natural it is, the better it will be.