Hi, not sure what kind of answer you need. But if you have a website or blog and it's featured with social bookmark icon, twitter for example, then just point the twitter icon to your twitter account.
that's all.

Cheers,

Irvan

Don't be spam and use any mathod to promote your site...

It depends upon the quality of bookmarking sites you are using.
If it's high quality an authority sites like delicious , stumbleupon, Reddit etc , You can bookmark your main site pages , I don't see any harm in that but if relatively low quality bookmarking sites, I will suggest to bookmark your web 2.0 properties or other layered pages

It depends on the social bookmarking site quality,
if the sites are high page rank then you can point the links to your main site!

Both are good but it's much better when you build links to your web 2.0 otherwise they can't do much to your ranking on their own..

I'm glad you asked this question I was wondering the same thing myself because it does seem to make more sense to make your web 2.0 properties rank higher in return creating higher quality backlinks for your main hub/website