sillybunny11486 is right. The Thread Tools drop down at the top of each thread allows you to subscribe to that particular thread.
As for removing existing subscriptions, if you go to your User CP, click List Subscriptions on the left, and then click List All Subscribed Threads, it should bring up a list of all of them. If you check the check box above the check boxes that correspond to individual threads you are subscribed to, it should select all of them for you at once. Then you can choose "Delete Subscription" from the Selected Threads action drop down.
This should allow you to easily remove all of your existing subscriptions.
As for removing existing subscriptions, if you go to your User CP, click List Subscriptions on the left, and then click List All Subscribed Threads, it should bring up a list of all of them. If you check the check box above the check boxes that correspond to individual threads you are subscribed to, it should select all of them for you at once. Then you can choose "Delete Subscription" from the Selected Threads action drop down.
This should allow you to easily remove all of your existing subscriptions.
