If you're aiming for perfect, "raw" prints that you won't finish later by sandpapering, painting or w/e, always remember of those three letters: Y/H/T
Imagine printing those letters standing up. Each relates to a particular problem:
Y is overhang angle. If you count from the vertical, anything higher than 45 degrees is likely to warp a bit or "fall" for not having enough support from the last layer, amongst other things. Some printers can get up to 60 degrees angle, with good cooling and plastic, but 45 is safer.
H is bridging, is how far the filament can go between two towers before falling of and stay "hanging". This one is only critical above a certain gap, but you'd do good to avoid anything bigger than 1cm if you're perfectionist.
T is similar to H, but just a horizontal part perpendicular to a tower. It's best avoided.
Although all printers can do supports like >>527102
mentioned, the filament is likely to lay hanging over them and get a bad finish. Since the support towers always skip the last layer before the actual surface to avoid fusing to the object, they are better used in models with 0.1mm~0.2mm layers or below. the bigger the layer height, bigger will be the gap between the support and the object.
But that's more printing design than 3d modeling technics actually. Usually anything watertight is good since the slicers have correction methods to fuse the objects. Besides that, always pay attention to your actual geometry WITHOUT SHADINGS/SMOOTHING GROUPS, since that's what will be printed. You're better served with high poly models if you want high fidelity.>Source: small business based on 3d printing and +2500h of printing under my belt