Sorry for the delayed response on this Martin.
The member subscription module is not something I've used much, as of yet anyways. So what I'm able to tell you might be a little limited. One thing that I know is fairly effective is including a subscribe or upgrade link within your menu itself. That can be done by going to your subscription page, copying the link, clicking on manage site, add page, external link page, and then use the link for your subscription page there. Name that pages link upgrade/subcribe, which ever works best for you, and then click save. That would be the way that would stand out the most in my view at least.
There may be other options already in place, but I've not used that system enough to know about them at this point. The best way to get some detailed info on this would be to ask in a support ticket. They will know all of the ins and outs or the system, and some of the best ways to use it and put it into place.
Sorry I couldn't be of more help myself, and here is a link to support.
