Stay away from the very edges of the screen to avoid aircraft appearing nearby and crashing immediately.
The shortest possible route is best. We have a natural urge to make a 'smooth' path, generally a curve. The aircraft in FlightControl can turn on a dime, make use of straight lines and extreme turns.
The faster the aircraft, the more potential for crashing. Prioritize the jumbo jets in order to get them off the screen faster, especially when things start to get crazy.
An undirected aircraft flies randomly. Direct all aircraft as quickly as possible. It's better to give an aircraft a sub-optimal route but have the landing scheduled than to stress yourself out trying to keep track of it.
Queue up aircraft destined for the same runway along the same path, where possible. Let the jumbo jets take the fore and normal jets bring up the rear, vice versa will get you rear-ended.
Don't worry about helicopter landings. The helipad is round and multiple helicopters can land simultaneously so long as they're approaching from different angles. Queue them up to go straight there and then only worry about dodging them.
Leave yourself some room for landing jets when a helicopter is flying parallel to the red runway. This is an exception to the straight-line rule. See above screenshot.
Work on timing. The different aircraft have predictable speeds; you should be able to draw paths for different types of jets to the red runway and have them land within close proximity to each other. Planes will often need to cross helicopter paths or go around them, you should be able to draw a safe path by predicting their flight.