You should start with everything (step 1, 2, and 3) suspended and unsuspend relevant cards as you go that are tagged for whichever exam you are studying for. If you’re studying for step 1, only unsuspend based on step 1 tags. If you’re studying for step 2, most people recommend suspending cards tagged for step 1 only and unsuspending cards tagged for step 2 and keep the step 1 cards you unsuspended for step 1 that are also tagged for step 2 going.