Allow for renewal of expired subscriptions by customer (expecially free trials)
You should make this process easier or you will likely lose a lot of would be customers. You should offer the ability to renew an expired subscription to a pay as you go plan once the free trial period expires (or really I think for any expired subscription). I was shocked to find that because I got busy the day my plan expired I had to contact support to get it renewed the next day (which they responded in 12 hours and had it renewed for me, which is great but shouldn't have had to log a support ticket for this). For getting initial customers in the door you should allow for renewal view the subscriptions screen (or someway to transfer all existing Azure services to another subscription). This wastes time for the customer and support staff.
In summary, offer a renew subscription button to expired / canceled subscriptions.
Yes especially considering I never wanted a free trial subscription and would have happily started with Pay As You Go but repeatedly got forced back to the free trial sign-up page so finally I just went with it.