The first way is to slowly pour water into the toilet as from a bucket.
The second way is to open the toilet tank lid and SLOWLY lift the flapper seal at the bottom of the tank until water begins to enter the bowl. Do not lift the flapper all the way up or else the toilet will flush.
If water goes down the toilet easily, the clog is cleared. If not, then try again by repeating the previous step and this step a time or two more.
If repeated attempts to clear the clog fail, then move on to the next step "Use the Closet Auger."