The number one factor when you choose which site to use is the kind of people already on the site. Sure, the site may have all the bells and whistles, but if it's full of people you wouldn't touch with a bargepole then perhaps it's not for you. Ask your colleagues in your target industry which sites they use and work from there.

Factor number two is what kind of site it is. Do you want to do business networking or social networking? Be aware that inviting your business colleagues to your social profile can have interesting results to say the least. For example, if you want to maintain your reputation as a staid, buttoned-up bastion of respectability, it's best not to invite your customers and co-workers to see you cavorting around in full Rocky Horror get-up.

Finally, do they offer the right mix of features? If you're bad with faces and names, then having contact's photographs in their profiles may be a killer feature. Likewise, if you're going to be combing through other people's networks, you'll want as much information as possible on their contacts.

So, which are the popular sites out there? Keep reading to find out...

If you're like me, you've probably already had millions of invitations to online networking sites like Facebook, MySpace, LinkedIn and so on. Why bother using these services? What can you get out of them?

• Findability - A lot of potential employers or customers now search professional networks like LinkedIn and Xing for the people they want to do business with. If you're not on there you could lose out on a great opportunity. Some of these sites also feed back into Google and other search engines, meaning it'll be even easier for people to find you.
• Staying organised - Instead of having to constantly update your database's contact details, just invite them to an online networking site and let them update it themselves.
• Finding people - Need to find a certain someone but don't know where to look? Maybe your existing contacts know someone. Sites like LinkedIn and Xing let you search your contacts' contacts to help you find the right people.
• Keeping up-to-date - Sites like LinkedIn and especially Facebook keep you constantly updated on your database's activity. If someone's changed jobs or left the country you can find out on the front page, without having to click through each individual profile to find out what's new.
• Following up - LinkedIn offers an invite tool that lets you insert individual names into a customisable stock invite. That means personalised follow-up letters and no more "Dear friend, it was nice meeting you at that event!".

Next time we'll be helping you decide which online networking service is best for you, or if you even need one at all. Until then, happy online networking!