Requirements:
1. land dwelling with decent mobility
2. complex object manipulation
3. optical and other sensory organ near the top, ideally quickly rotatable
4. symmetric

Occam's razor solutions :
1. two legs (maybe four)
2. two (maybe four) arms and fingers
3. head and a neck

= basically humanoid shape
we have the intelligent planet dominating species basic bitch starter pack body shape

sci-fi from the didn't get aliens wrong (except for truly ridiculous shit like cross-breeding), and people who say otherwise are hipster faggots.