There is No Magic Highlighter for All Hair
Highlights are great, but there is not a simple one color highlight solution for everyone. Unless you are a college dude who just wants to have yellow hair for the summer, you should get some consultation on what color of highlights to get and basic placement of them as well.
Get Some Ideas
This is something I rarely have to remind women to do, but just in case, search the internet or magazines for hair styles you like with face shapes and skin tones similar to yours. It's important to be able to picture yourself with a style you like as well as one you can actually achieve.
Ask Your Hairdresser Before
Springing a new idea on the person who is ready to do the usual isn't always the best idea. Granted, most hairdressers are expecting the client to have some changes in mind, but give them a little prep time so it doesn't turn into a last minute rush job. Again, not only is color important, but placement as well.