Use 3MF format for printing when possible It doesn't convert the file to triangles and keeps more detail in a smaller file-size
Filaments:

• PLA for tests and aesthetic parts
• PETG for some mechanical strength and durability
• ABS/ASA for more rigidity
• TPU for flexible parts (prints extremely slow)

More Walls/Perimeters for strength (up to around 7) Most printers can print up to 50° overhangs without support, depending on material.
Prints are a lot stronger in the XY-Plane
More infill for Stiffness (up to around 50%)
As little support as possible

• on flat spots snug supports
• on irregular shapes tree supports

Use a brim for small parts or parts that could fall over, it improves bed adhesion
Small chamfers on all edges make the print look way nicer