When getting backlinks, should I point them to https://www.site.com or http://www.site.com? for reference, when someone goes on my site by typing in http://www.site.com or www.site.com they get redirected to https://www.site.com. Also, please note that all pages on our site have a secure 's' in them, example https://www.site.com/blog thanks
If you are always going to have HTTPS running on your site I would build up all your links using HTTPS. I assume if someone hits your homepage your web server, htaccess or some script is forcing it to HTTPS, this typically results in a permanent 301 redirect. So in theory the search engines should recognize that and be OK with it.
BUT - at least in the past search engines looked at http and https as separate sites.
I would link to the HTTPS page for consistency and so all incoming responses don't have to have a 301 redirect sent to the browser and sent over to the new page.
That is if your site is always going to be 100% https for all URLs. Then just link to that.