Use all the features
Take advantage of all the features like HTML and special fonts.  Use every option they offer.  If they have a blog then use it.  Make comments, too.

Don’t sell
Avoid outright selling.  This is usually not allowed and could get you banned.  Instead put up your link and tell about what you do.  That is allowed.

Be professional but friendly
Always be professional, but also be a friendly person.  If people ever get the vibe that you are there to sell they will likely back off.

Go public
Most of these sites allow you to make your profile private.  That will defeat your purpose so you need to make sure your profile is public for everyone to see.

Visit others pages
Travel around the site.  Look at other people’s pages.  Learn about them and seek out friends.