Therefore if you either tire from answering or ignoring all the wrong people and if you want to improve the interest shown to you from qualified respondents, then start by using your header to filter out the riff . For example: If you know you want a person of a certain age, ask for it.
Though it is best to be positive rather than negative in your online dating profile, header included, you may be able to jokingly pull off the need-not-apply header. "Looking for fit 24-30 year old male within 20 miles of Los Angeles".
The rules do not change as much as you may think they would for online dating. As much as some people would love to think, using all capital letters does not drive people to click on your profile. Using caps lock should only be used when YOU ARE YELLING AT SOMEONE OVER THE INTERNET!
The profile header, as such, is that opening line for any date. Generally, all capital letter headlines just scream for negative attention.
By creating a filter, when a person who doesn't match your criteria reads your header they are likely to continue on.