Against aatrox, Use the minion wave to block Aatrox from landing his W and going for the all-in. Always ensure that there is at least 1 minion between you and him at all times. 
 
Both his Q and E have rather long cooldowns in the early game. If he uses them, try to abuse the cooldowns and look to trade with him while they’re down.
 
If you’re ranged, use your range advantage to harass him with basic attacks whenever he walks forward to last hit. Do not over-commit or get too close to him though when trying to harass. Against aatrox, Use the minion wave to block Aatrox from landing his W and go for all-in. Always make sure there's at least 1 minion between you and him at all times. Both his Q and E have a long enough cooldowns in early play. If he uses them, try to abuse cooldowns and look to trade with him while they're down. If you're varied, use your range advantage to harass him with basic attacks when he's walking forward for the last shot.