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@Rafi : I want to explicity state in the .htaccess rule that a 301 must be used.

Thank you for your reply @TomRoberts
How can I make sure it's a 301 permanent redirect ?

What's the best practice to switch from an all HTTP site to an all HTTPS site ?
No changes to the site structure, just a full site switch to SSL.
Right now, the site is reachable with HTTP and with HTTPS.

http://crocodesign.be --> https://crocodesign.be
http://www.crocodesign.be --> https://crocodesign.be
https://www.crocodesign.be --> https://crocodesign.be

CMS : Wordpress 3.9
Server type : Apache
Preferred method : .htaccess

Google considers both url's as different.

In your use case, i would use a robots.txt file to prevent google from indexing the site / pages. 
When the site is released and the url's are permanent, you can remove the robots.txt

More about robots.txt : http://en.wikipedia.org/wiki/Robots_exclusion_standard

As a webdesigner, I tend to place a link to my website in the footer of sites I build.
I consider this a form of brand awareness and reputation building, with nice SEO benefits.

What is the SEO best practice in this case ? Link to a page in your portfolio describing your work on the site ? Sending all the links to the homepage ? What about the link text ?

That was my first thought as well, but the data doesn't support it.

• Dashboard --> Traffic to your site : 9 from other
• Search --> Traffic from search : 6 from (not provided)

Even if 6 out of 9 are from not provided, that doesn't explain where the other 3 visits come from.
Might be that the other 3 are from links in mails or newsletters, how are those displayed in Moz Analytics ?

You can use the new HTML5 tags

<header>

<footer>

<aside>.
They work the same as a, but give more information to Google.

• http://www.w3schools.com/tags/tag_header.asp (Header)
• http://www.w3schools.com/tags/tag_footer.asp (Footer)
• http://www.w3schools.com/tags/tag_aside.asp (Sidebar)

</aside>

</footer>

</header>

What is the "other" group in traffic to your site on the moz analytics dashboard ?

"Not provided" is in search - organic search history so it's not that.

You can use the new HTML5 tags

<header>

<footer>

<aside>.
They work the same as a, but give more information to Google.

• http://www.w3schools.com/tags/tag_header.asp (Header)
• http://www.w3schools.com/tags/tag_footer.asp (Footer)
• http://www.w3schools.com/tags/tag_aside.asp (Sidebar)

</aside>

</footer>

</header>

Google considers both url's as different.

In your use case, i would use a robots.txt file to prevent google from indexing the site / pages. 
When the site is released and the url's are permanent, you can remove the robots.txt

More about robots.txt : http://en.wikipedia.org/wiki/Robots_exclusion_standard