As more 30- and 40-somethings login to Facebook, begin to Tweet, add their credentials to LinkedIn and post pictures of their family vacations to Flickr, it becomes harder to separate your work and personal personae. And as more employers begin to use these social networking sites to vet their new hires – assuming that people will start to have new hires at some point in the future once this miserable economy turns around – the situation is only going to get worse.

What got me started thinking more about this was that I am giving a speech next week to show people how to make the most of LinkedIn, one of the leading social sites that is used by a wide variety of professionals to look for work and polish your resume, qualifications and recommendations from previous employers. Granted, this is not a new topic – people have been having problems with what they say online for years. Heather Armstrong, who’s Web site dooce.com created the verb that is used when someone is fired over their blog, was fired over her blog many years ago (her new book is a real treat and a collection of some of her writings that is a true joy to read). Now dooce.com generates thousands of dollars a month in ad revenue. That is taking lemons and turning them into not just lemonade, but Absolut Lemon, or maybe even Absolut Gold.

So here are some recommendations for those of you that are new to this whole Internet thing, to pass along to your less-clueful friends and relatives.

First, keep sex, politics, religion, and family out of your online life to the extent that you can. If you feel that you have to tell the world about these things, think about how a potential future employer might react to seeing this stuff in your profile. No one really wants to know that you are a member of the “Republican Party of the Virgin Islands” (as one of my Facebookers put it), whatever that means. Another friend is in a committed relationship with his dog, again, not something I really want to find out the details. And those married folks that indicate that they would enjoy having relations with a third party are just too icky for me. Leave some blanks spaces in your profile in these areas. Too much information!

Second, tell the truth. If you are single and looking for love, then by all means go online and do your thing and misrepresent yourself however you see fit or whatever you think will attract potential partners. But when it comes to talking about your professional accomplishments, don’t exaggerate, invent new job titles, degrees, or whatever other credentials that you don’t have. It isn’t worth it, and eventually it will come back to hurt you or prevent you from getting that plum job that you covet. There is also no need to document every waking and sober moment since college either: just hit the most recent highlights for now. And when it comes to those non-sober moments, leave that info on the cutting room floor. No one really wants to see your expertise with using beer bongs.

Third, if you are one of the unfortunate ones who are presently between jobs, make LinkedIn and other sites part of a daily ritual. Whether you spend a few minutes or hours isn’t all that important, just so that you spend some regular time updating your profile and seeking out to expand your network.

Fourth, decide on what your “friending” policy is going to be and be consistent, at least for inside each social site that you frequent. For example, I am most stringent with the people that want to network with me on LinkedIn, and only accept connections with people that I have actually met face to face, or who have been long-time email correspondents. I also routinely refuse connections from headhunters and HR people, because I am not interested in enriching their businesses with my connections. But on Facebook, I have a more liberal friending policy, just because.

Finally, spend some time thinking about how you acquired your existing professional friends: do you like to meet and greet at industry conferences? Are you more of a small group or large group socializer? Do you prefer one-on-one situations? Did you ever co-author anything and enjoy/detest the experience? Do you tend to keep work colleagues around for many years that last past the time on the job? Were you popular in junior high or peaked in sophmore year? Do you still stay in touch with your frat brothers or sorority sisters?

Remember that most of us are still pretty new at MyBook and Friendspace and that even Oprah did her first Tweet in ALL CAPS. Do experiment and try different strategies, and feel free to share what works for you if that is appropriate. Just don’t send me any links to those toga party pix.