You may have 2 links per hub to any one domain. A second domain can have another 2 links and so one. An RSS feed counts as 2 links. The domain HubPages dot com is exempted from this rule, as are most true authority sites such as Wikipedia.
Be aware though, that if a large percentage of your hubs all point to the same domain your whole account will be considered as over promotional and unpublished.
you can put 1 or 2 links when writing a blog
You can have many links ( 2-4 ) but at the same time your blog must have new contents updated in regular time period.
you can put multiple links to your blog but they should be genuine and they should be increase your blog quality....
i read google doesnt like it if you put a new link to your new blog every day. how long do i have to wait before adding a link? will once a week be ok? once every two weeks? once a month?