The sign for "guess" starts with a splayed 5-hand to the side/front of the head that moves across/in-front-of your face and ends up in an "S"-handshape.
GUESS:
Now, if you are thinking, "Wait, the sign for 'guess' looks a lot like one of the versions of the sign for 'MISS,'" -- you are correct.
Those two signs (guess and miss) are done almost the same. The specific meaning is going to rely heavily on context (the rest of your sentence and the situation) and your facial expression.
MISS-(fail to hit, reach, catch, meet, or otherwise make contact with)
Note:
The English concept of "miss" has other meanings and another sign variation. For the version of "miss" that means the emotion of missing someone see: MISS
Notes: